Related to  #11474 and #12815.

The following should be added to `package.json` of `pdfjs-dist` for `worker-loader`.
```
  "peerDependenciesMeta": {
    "worker-loader": {
      "optional": true
    }
  }
```

npm v7 installs `peerDependencies` by default. We can see that calling `npm install pdfjs-dist` in an empty directory will install `webpack` and others in `node_modules`.

> In npm versions 3 through 6, peerDependencies were not automatically installed, and would raise a warning if an invalid version of the peer dependency was found in the tree. As of npm v7, peerDependencies are installed by default.

- https://docs.npmjs.com/cli/v7/configuring-npm/package-json#peerdependencies
- https://github.blog/2020-10-13-presenting-v7-0-0-of-the-npm-cli/

We can make `worker-loader` optional with `peerDependenciesMeta`.

- https://docs.npmjs.com/cli/v7/configuring-npm/package-json#peerdependenciesmeta
- https://github.com/npm/rfcs/issues/221
"Safari >= 11.1",
    "> 0.5%",
    "not IE > 0",
    "not dead",
  ],
};
const DEFINES = Object.freeze({
  PRODUCTION: true,
  SKIP_BABEL: true,
  TESTING: false,
  
  GENERIC: false,
  MOZCENTRAL: false,
  CHROME: false,
  MINIFIED: false,
  COMPONENTS: false,
  LIB: false,
  IMAGE_DECODERS: false,
});
function transform(charEncoding, transformFunction) {
  return through.obj(function (vinylFile, enc, done) {
    const transformedFile = vinylFile.clone();
    transformedFile.contents = Buffer.from(
      transformFunction(transformedFile.contents),
      charEncoding
    );
    done(null, transformedFile);
  });
}
function safeSpawnSync(command, parameters, options) {