This moves/exposes the `URL` polyfill similarily to the existing `ReadableStream` polyfill, rather than exposing it globally, to avoid interfering with any "outside" code.
Both the `URL` and `ReadableStream` polyfills are now exposed on the `pdfjsLib` object, such that they are accessible to the viewer components.
Furthermore, the `no-restricted-globals` ESLint rule is also enabled to prevent accidental usage of the native `URL`/`ReadableStream` implementations directly in the `src/` and `web/` folders; see also https://eslint.org/docs/rules/no-restricted-globals
Addresses the remaining TODO in https://github.com/mozilla/pdf.js/projects/6
Please note that the standalone `pdf.image_decoders.js` file will be including the complete `src/shared/util.js` file, despite only using parts of it.[1] This was done *purposely*, to not negatively impact the readability/maintainability of the core PDF.js code.
Furthermore, to ensure that the compatibility is the same in the regular PDF.js library *and* in the the standalone image decoders, `src/shared/compatibility.js` was included as well.
To (hopefully) prevent future complaints about the size of the built `pdf.image_decoders.js` file, a few existing async-related polyfills are being skipped (since all of the image decoders are completely synchronous).
Obviously this required adding a couple of pre-processor statements, but given that these are all limited to "compatibility" code, I think this might be OK!?
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[1] However, please note that previous commits moved `PageViewport` and `MessageHandler` out of `src/shared/util.js` which reduced its size.
