Follow up on #32, minimize future diffs

[floesche]

Follow up on #32. Having this in main and then using the .prettierrc as the definition of what the code looks like, increases readability of code and code changes.

[mbreiser]

Thanks for this, Frank — agreed that having main match .prettierrc makes diffs cleaner, and I'd like to land it. One ask before we merge:

71 of the 100 files are third-party vendored dependencies, not our code:

• js/vendor/yaml/** (70 files) — the yaml npm package (Eemeli Aro, ISC); our checked-in copy that experiment_designer_v3.html imports.
• js/gif.worker.js — jnordberg's gif.js worker (prettier un-minified it from 3 lines → ~886).

Reformatting these actually works against "minimize future diffs": once we restyle vendored yaml, every future version bump (2.9 → 2.10 …) diffs against our reformatted copy instead of upstream, burying real changes in style noise. And un-minifying the gif worker just bloats it for no benefit.

Could you add a .prettierignore and re-run npm run format?

# Vendored / third-party — keep byte-identical to upstream
js/vendor/
js/gif.worker.js

That drops the PR to ~29 first-party files (the part worth reviewing), and stops npm run format from churning vendored code going forward (it currently globs **/*.js, which is why this happened). The first-party-only reformat looks good to me — happy to merge as soon as it's rescoped. Thanks!

[floesche]

I moved the gif.worker.js file to vendor, but otherwise followed the suggestion.