feat(build)!: Introduce ESM entrypoints (#8091)

* feat(build)!: Introduce ESM entrypoints for chunks

  Introduce an "import" conditional export for each of the chunk
  entrypoints (blockly/core, blockly/blocks, blockly/javascript
  etc.), and point these at wrappers created by build_tasks.js
  that import the corresponding <chunk>_compressed.js file and
  export its named exports.

  BREAKING CHANGE:

  Importing Blockly via

      import Blockly from 'blockly/core';

  (and similarly for the other chunk entrypoints) has worked until
  now because most build tools (including Webpack in particular)
  fuilfil the request for the default export of a CJS module by
  providing the module.exports object, rather than an
  explicitly-named default export as they would for an ES module.

  Since core/blockly.ts (the notional entrypoint for blockly/core)
  does not provide a default export, the wrappers created by this
  PR do not either.

  Code of the above form will therefore break, and should be updated
  to use a wildcard:

      import * as Blockly from 'blockly/core';

* feat(build)!: Introduce main package ESM entrypoint

  Introduce an "import" conditional export for the top-level
  package entrypoint (blockly), and point it at a wrappers
  created by build_tasks.js that imports the existing index.js
  file.

  BREAKING CHANGE:

  Importing Blockly via

      import Blockly from 'blockly';

  has worked until now because most build tools (including Webpack
  in particular) fuilfil the request for the default export of a
  CJS module by providing the module.exports object, rather than an
  explicitly-named default export as they would for an ES module.

  Since core/blockly.ts does not provide a default export, the
  wrapper created by this PR does not either.

  Code of the above form will therefore break, and should be updated
  to use a wildcard:

      import * as Blockly from 'blockly';

* feat(build)!: Introduce ESM entrypoints for langfiles

  Introduce an "import" conditional export for each of the
  langfile entrypoints (msg/en, msg/fr, etc.),, and point them
  at wrappers created by build_tasks.js that import the
  existing <lang>.js file.

  BREAKING CHANGE:

  Importing languages via

      import en from 'blockly/msg/en';

  has worked until now because most build tools (including Webpack
  in particular) fuilfil the request for the default export of a
  CJS module by providing the module.exports object, rather than an
  explicitly-named default export as they would for an ES module.

  Code of the above form will therefore break, and should be updated
  to use a wildcard:

      import * as en from 'blockly/msg/en';

* fix(typings): Remove bogus .d.ts file.

  For some reason we had a typings/msg/yue.d.ts that did not
  correxpond to any msg/json/yue.json.  Delete it.

package.json

@@ -57,40 +57,49 @@
   "exports": {
     ".": {
       "types": "./index.d.ts",
+      "import": "./index.mjs",
       "umd": "./blockly.min.js",
       "default": "./index.js"
     },
     "./core": {
       "types": "./core.d.ts",
       "node": "./core-node.js",
+      "import": "./blockly.mjs",
       "default": "./blockly_compressed.js"
     },
     "./blocks": {
       "types": "./blocks.d.ts",
+      "import": "./blocks.mjs",
       "default": "./blocks_compressed.js"
     },
     "./dart": {
       "types": "./dart.d.ts",
+      "import": "./dart.mjs",
       "default": "./dart_compressed.js"
     },
     "./lua": {
       "types": "./lua.d.ts",
+      "import": "./lua.mjs",
       "default": "./lua_compressed.js"
     },
     "./javascript": {
       "types": "./javascript.d.ts",
+      "import": "./javascript.mjs",
       "default": "./javascript_compressed.js"
     },
     "./php": {
       "types": "./php.d.ts",
+      "import": "./php.mjs",
       "default": "./php_compressed.js"
     },
     "./python": {
       "types": "./python.d.ts",
+      "import": "./python.mjs",
       "default": "./python_compressed.js"
     },
     "./msg/*": {
       "types": "./msg/*.d.ts",
+      "import": "./msg/*.mjs",
       "default": "./msg/*.js"
     }
   },