Packages: Extract viewport package

[gziolo]

Part of #3955.

This PR moves viewport module to packages folder and converts it to npm package maintained by Lerna. It's mostly boils down to moving files. In addition, I had to add package.json file and a few small adjustments to the existing setup.

There are NO breaking changes

I also added a few unrelated changes where I discovered that we didn't list dev dependencies in other packages.

Testing instructions

• Make sure the tests pass without regression
• Make sure that editor still works

[youknowriad]

Straightforward 👍

[youknowriad]

I guess it's not that important but I thought we were using -beta.0 for the first unpublished versions. Since we publish stable versions directly, it's not very important.

[gziolo]

I think we are going to publish 1.0.0 later this week for all packages to make publishing with 2FA maintinanable 😄

[aduth]

I think this may have broken npm run docs:build:

> [email protected] docs:build /Users/andrew/Documents/Code/vvv/www/editor/htdocs/wp-content/plugins/gutenberg
> node docs/tool

fs.js:646
  return binding.open(pathModule._makeLong(path), stringToFlags(flags), mode);
                 ^

Error: ENOENT: no such file or directory, open '/Users/andrew/Documents/Code/vvv/www/editor/htdocs/wp-content/plugins/gutenberg/viewport/store/selectors.js'
    at Object.fs.openSync (fs.js:646:18)
    at Object.fs.readFileSync (fs.js:551:33)
    at namespaceConfig.(anonymous function).forEach (/Users/andrew/Documents/Code/vvv/www/editor/htdocs/wp-content/plugins/gutenberg/docs/tool/parser.js:25:21)
    at Array.forEach (<anonymous>)
    at forEach (/Users/andrew/Documents/Code/vvv/www/editor/htdocs/wp-content/plugins/gutenberg/docs/tool/parser.js:24:28)
    at Array.forEach (<anonymous>)
    at Object.entries.forEach (/Users/andrew/Documents/Code/vvv/www/editor/htdocs/wp-content/plugins/gutenberg/docs/tool/parser.js:23:30)
    at Array.forEach (<anonymous>)
    at module.exports (/Users/andrew/Documents/Code/vvv/www/editor/htdocs/wp-content/plugins/gutenberg/docs/tool/parser.js:15:27)
    at Object.<anonymous> (/Users/andrew/Documents/Code/vvv/www/editor/htdocs/wp-content/plugins/gutenberg/docs/tool/index.js:14:23)

[gziolo]

Right, I should remove it from yet another list of non-package modules 😃
This line: https://github.com/WordPress/gutenberg/blob/master/docs/tool/config.js#L23

And also path to store folder is outdated now.

[gziolo]

@aduth, the issue was fixed in #7994.