feat(presence-tracker): Add "reactions" using presence notifications

[tylerbutler]

Summary of changes

The presence-tracker example now uses the notifications infrastructure from the presence package to send "reactions" to other clients. Users can select any emoji from an emoji picker, and any left click in the window will send the reaction to other users. Other clients will see the reaction animate and fade out.

Implementation notes

• Unlike the mouse and focus trackers, I did not create a class to manage things. Instead, I just wrote an init function that initializes the reactions for the whole app. I think this makes it a little easier to see how things fit together, but could be refactored if needed.
• The emoji picker element has a bug with node16 module resolution. The fix is straightforward so I just patched the local dep. Upstream fix PR is already opened.
• I considered a smaller/more limited reaction selection UX, but the emoji picker was easy to adopt, so I went with that.

Known issues

• TODOs to check connection status before sending.
• No testing - not sure how to do it or if it's worth it since we have tests on notifications themselves already.

[github-actions]

🔗 No broken links found! ✅

Your attention to detail is admirable.

linkcheck output

> fluid-framework-docs-site@0.0.0 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"


> fluid-framework-docs-site@0.0.0 serve
> docusaurus serve --no-open

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

> fluid-framework-docs-site@0.0.0 check-links
> linkcheck http://localhost:3000 --skip-file skipped-urls.txt

Crawling...

Stats:
  170508 links
    1603 destination URLs
    1842 URLs ignored
       0 warnings
       0 errors

[alexvy86]

A couple of small things, otherwise LGTM. Disclaimer: I might not be the target audience you were interested in for a "new eyes" review, I've dealt a bit with the presence framework before for the ai-collab example app.

[alexvy86]

The fix was merged and released yesterday, no more need for a patch 🥳

[alexvy86]

Do we plan to exercise the "intense" case? If not I'd say remove it to keep things simple.