Support PDF annotation

[personalizedrefrigerator]

Summary

Adds support for PDF annotation through a new @js-draw/pdf-support package. This package exposes an interface that must be implemented for whichever PDF backend is to be used.

To-do

• Refactor MuPDF-related logic out of docs/examples/pdf-support and into a package that can be published to NPM.
  • Note: MuPDF is licensed under the GNU AGPLv3 — it will need to be made clear that this is the case in the package's README.
• Better page memory management.
  • Page images should be freed if not recently used.
  • Support caching pages at different zoom levels, perhaps by forcing the use of [js-draw's rendering cache?](https://github.com/personalizedrefrigerator/js-draw/blob/main/packages/js-draw/src/rendering/caching/RenderingCache.
• Support image annotations
• Support highlight annotations
• Support searching for PDF text
• (Optional/follow-up PR) Support selecting PDF text
• (Optional/follow-up PR) Support links
• (Optional/follow-up PR) Support form conrols
• (Optional) More memory-efficient saving of strokes.

[github-actions]

Visit the preview URL for this PR (updated for commit d42234c):

https://js-draw--pr67-work-pdf-support-r8ae15qu.web.app

_{(expires Thu, 04 Apr 2024 21:29:12 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

_{Sign: e560ee6f7bb6b79cb55b42fb4c05e9fd1b5c506e}