Blob placeholders prototype

[ChumpChief]

Prototype branch for blob placeholders. Replaces #24137 which has more context.

[dannimad]

Is there any design doc, one pager or context to help review this approach? I believe I get the general idea through spare conversations but a written starting point would be great and I'd appreciate a pointer in case it already exists.

[github-actions[bot]]

🔗 No broken links found! ✅

Your attention to detail is admirable.

linkcheck output

> [email protected] ci:check-links /home/runner/work/FluidFramework/FluidFramework/docs
> start-server-and-test "npm run serve -- --no-open" 3000 check-links

1: starting server using command "npm run serve -- --no-open"
and when url "[ 'http://127.0.0.1:3000' ]" is responding with HTTP status code 200
running tests using command "npm run check-links"


> [email protected] serve
> docusaurus serve --no-open

[SUCCESS] Serving "build" directory at: http://localhost:3000/

> [email protected] check-links
> linkcheck http://localhost:3000 --skip-file skipped-urls.txt

Crawling...

Stats:
  163664 links
    1315 destination URLs
    1547 URLs ignored
       0 warnings
       0 errors

[ChumpChief]

This feature has been checked in already, as of #24458 - prototype branch is no longer needed.