Migrate to ecmarkup

This is the first step to revamp this repo: [ecmarkup](https://github.com/tc39/ecmarkup)
is TC39's official tool for specifying syntax and semantics for ECMAScript.
I proposed that we should adopt it because it has several favorabilities
than the current approach (`README.md` + a `gh-pages` website living in
the `websitescript` branch):
1. The resultant `index.html` has a similar looks and feels with the
   official ECMA-262 spec.
2. It uses [Grammarkdown](https://github.com/rbuckton/grammarkdown)
   which is not only convenient to write but more importantly, can
   enforce the grammar to be more formal.
3. It provides links to ECMA-262 out of the box (closed facebook#112).
   Furthurmore, I can use `<ins>` to make "extension" points explicit.

One possible concern it that it'll make this too like a ECMAScript proposal,
but I think we mediated by opting-out from the "stage-N proposal"
heading, and by explicitly calling out our intention in the
"Introduction" section.

In addition,
- Link to JXON is updated since the original link no more existed.
- Parser and Transpiler section is dropped from the "spec" website.
- Facebook, Inc. is updated to Meta Platform, Inc everywhere.

Once this is merged, we can switch to `main` to host Github Pages.

.gitignore

@@ -0,0 +1,43 @@
+# Logs
+logs
+*.log
+npm-debug.log*
+
+# Runtime data
+pids
+*.pid
+*.seed
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (http://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules
+jspm_packages
+
+# Optional npm cache directory
+.npm
+
+# Optional REPL history
+.node_repl_history
+
+# Only apps should have lockfiles
+yarn.lock
+package-lock.json
+npm-shrinkwrap.json
+pnpm-lock.yaml

README.md

@@ -1,7 +1,8 @@
 DRAFT: JSX Specification
 ========================
 
-JSX is an XML-like syntax extension to ECMAScript without any defined semantics. It's NOT intended to be implemented by engines or browsers. __It's NOT a proposal to incorporate JSX into the ECMAScript spec itself.__ It's intended to be used by various preprocessors (transpilers) to transform these tokens into standard ECMAScript.
+
+JSX is an XML-like syntax extension to ECMAScript without any defined semantics. It's NOT intended to be implemented by engines or browsers. __It's NOT a proposal to incorporate JSX into the ECMAScript spec itself.__ It's intended to be used by various preprocessors (transpilers) to transform these tokens into standard ECMAScript. 
 
 ```jsx
 // Using JSX to express UI components.
@@ -18,6 +19,11 @@ var dropdown =
 render(dropdown);
 ```
 
+[See grammar and spec text](https://facebook.github.io/jsx).
+
+
+
+
 Rationale
 ---------
 
@@ -31,139 +37,6 @@ It is our intention to claim minimal syntactic real estate while keeping the syn
 
 This specification does not attempt to comply with any XML or HTML specification. JSX is designed as an ECMAScript feature and the similarity to XML is only for familiarity.
 
-Syntax
-------
-
-_JSX extends the PrimaryExpression in the [ECMAScript 6th Edition (ECMA-262)](https://www.ecma-international.org/ecma-262/8.0/index.html) grammar:_
-
-PrimaryExpression :
-
-- JSXElement
-- JSXFragment
-
-__Elements__
-
-JSXElement :

-
-- JSXSelfClosingElement

-- JSXOpeningElement JSXChildren<sub>opt</sub> JSXClosingElement  
-  (names of JSXOpeningElement and JSXClosingElement should match)
-
-JSXSelfClosingElement :
-
-- `<` JSXElementName JSXAttributes<sub>opt</sub> `/` `>`
-
-JSXOpeningElement :
-
-- `<` JSXElementName JSXAttributes<sub>opt</sub> `>`
-
-JSXClosingElement :
-
-- `<` `/` JSXElementName `>`
-
-JSXFragment :
-
-- `<` `>` JSXChildren<sub>opt</sub> `<` `/` `>`
-
-JSXElementName :
-
-- JSXIdentifier
-- JSXNamespacedName
-- JSXMemberExpression
-
-JSXIdentifier :
-
-- IdentifierStart
-- JSXIdentifier IdentifierPart
-- JSXIdentifier __NO WHITESPACE OR COMMENT__ `-`
-
-JSXNamespacedName :
-
-- JSXIdentifier `:` JSXIdentifier
-
-JSXMemberExpression :
-
-- JSXIdentifier `.` JSXIdentifier
-- JSXMemberExpression `.` JSXIdentifier
-
-__Attributes__
-
-JSXAttributes :

-
-- JSXSpreadAttribute JSXAttributes<sub>opt</sub>
-- JSXAttribute JSXAttributes<sub>opt</sub>
-
-JSXSpreadAttribute :
-
-- `{` `...` AssignmentExpression `}`
-
-JSXAttribute :

-
-- JSXAttributeName JSXAttributeInitializer<sub>opt</sub>
-
-JSXAttributeName :
-
-- JSXIdentifier
-- JSXNamespacedName
-
-JSXAttributeInitializer :

-
-- `=` JSXAttributeValue
-
-JSXAttributeValue :

-
-- `"` JSXDoubleStringCharacters<sub>opt</sub> `"`
-- `'` JSXSingleStringCharacters<sub>opt</sub> `'`
-- `{` AssignmentExpression `}`
-- JSXElement
-- JSXFragment
-
-JSXDoubleStringCharacters :

-
-- JSXDoubleStringCharacter JSXDoubleStringCharacters<sub>opt</sub>
-
-JSXDoubleStringCharacter :

-
-- SourceCharacter __but not `"`__
-
-JSXSingleStringCharacters :

-
-- JSXSingleStringCharacter JSXSingleStringCharacters<sub>opt</sub>
-
-JSXSingleStringCharacter :

-
-- SourceCharacter __but not `'`__
-
-__Children__
-
-JSXChildren :

-
-- JSXChild JSXChildren<sub>opt</sub>
-
-JSXChild :
-
-- JSXText
-- JSXElement
-- JSXFragment
-- `{` JSXChildExpression<sub>opt</sub> `}`
-
-JSXText :
-
-- JSXTextCharacter JSXText<sub>opt</sub>
-
-JSXTextCharacter :
-
-- SourceCharacter __but not one of `{`, `<`, `>` or `}`__
-
-JSXChildExpression :
-
-- AssignmentExpression
-- `...` AssignmentExpression
-
-__Whitespace and Comments__
-
-_JSX uses the same punctuators and braces as ECMAScript. WhiteSpace, LineTerminators and Comments are generally allowed between any punctuators._
-
 Parser Implementations
 ----------------------
 
@@ -255,7 +128,7 @@ The JSX syntax is similar to the [E4X Specification (ECMA-357)](http://www.ecma-
 License
 -------
 
-Copyright (c) 2014 - present, Facebook, Inc.
+Copyright (c) 2014 - present, Meta Platform, Inc.
 All rights reserved.
 
 This work is licensed under a [Creative Commons Attribution 4.0