fix: adjust browser build to MathJax v4

Work in progress, cf. the discussion at mathjax/MathJax#3086

components/config.json

@@ -0,0 +1,18 @@
+{
+  "build": {
+    "id": "[ams]/unicode-math",
+    "component": "input/tex/extension/unicode-math",
+    "js": "../js",
+    "ts": "../ts",
+    "targets": ["unicode-math.ts"]
+  },
+  "webpack": {
+    "name": "unicode-math",
+    "js": "../js",
+    "libs": [
+      "components/src/input/tex-base/lib",
+      "components/src/core/lib"
+    ],
+    "dist": "../browser/"
+  }
+}

components/unicode-math.js

@@ -0,0 +1 @@
+import './lib/unicode-math.js'; // NOTE magical path for MathJax's build process

package.json

@@ -27,7 +27,7 @@
     "fromTeX": "cd bin && perl make_maps && perl make_test",
     "pretest": "npx tsc",
     "test": "node test/base.js && node test/corrections.js",
-    "build": "npx tsc &&  node ./node_modules/mathjax-full/components/bin/makeAll"
+    "build": "npx tsc &&  node ./node_modules/mathjax-full/components/bin/makeAll --mjs components"
   },
   "devDependencies": {
     "jsdom": "19.0.0",

test/unicode-math-browser.html

@@ -11,15 +11,15 @@
     MathJax = {
        loader: {
           load: ['[test]/unicode-math.js'],
-          paths: {test: '../browser/'}
+          paths: {test: '../browser'}
        },
        tex: {
           packages: {'[+]': ['unicode-math']}
        }
     };
     </script>
     <script type="text/javascript" id="MathJax-script" async
-      src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-chtml.js">
+      src="https://cdn.jsdelivr.net/npm/mathjax@4.0.0-beta.3/tex-chtml.js">
     </script>