In Gulp 4, which we use for years now, the `gulp.src()` function
supports the `removeBOM` option to disable the default BOM stripping,
so this commit uses that to get rid of our `vinyl-fs` dependency.
Note that this actually makes disabling BOM stripping work again. It's
currently broken because in `vinyl-fs` 3, that we already use since 2018
in commit 95de23e, the `stripBOM` option was renamed to `removeBOM`, so
the current code doesn't actually disable BOM stripping which we now
confirmed and sadly broke for years without anyone noticing. Most likely
this is because the BOM is not required for UTF-8 documents, but while
not necessary it also can't hurt to have it for tools that use it to
determine if a document is UTF-8.
Trying to update Stylelint to version `15.10.1`, and beyond, broke linting. Looking at the changes the issue appears to be that the `bin/stylelint.js` file was replaced with `bin/stylelint.mjs` instead, which our `gulp lint` runner wasn't able to automatically find; see https://github.com/stylelint/stylelint/compare/15.10.0...15.10.1
By leveraging import maps we can get rid of *most* of the remaining `require`-calls in the `src/display/`-folder, since we should strive to use modern `import`-statements wherever possible.
The only remaining cases are Node.js-specific dependencies, since those seem very difficult to convert unless we start producing a bundle *specifically* for Node.js environments.
In the last couple of years we've been quicker to remove support for older browsers/environments, which means that at this point in time we don't bundle that many polyfills. (The polyfills are also generally simpler nowadays, ever since we removed support for e.g. Internet Explorer.)
Rather than having to *manually* handle the polyfills, we can actually let Babel take care of bundling the necessary polyfills for us; please refer to https://babeljs.io/docs/babel-preset-env
The only exception here is the Node.js-specific compatibility-code, which is moved into the `src/display/node_utils.js` file. This ought to be fine since workers are not available/used in Node.js-environments.
*Please note:* For the `legacy`-builds this will increase the size of the *built* files, however that seems like a very small price to pay in order to simplify maintenance of the general PDF.js library.
