DX: Browser plugin preview

[macintoshhelper]

• [WIP] webpack config setup for fast refresh + websocket server

• add prod/dev hmr webpack config option

• render immediately and handle AsyncMessage in startup app hook

• forward ui AsyncMessages to browser via WebSockets

• null check sentry transaction to fix browser error

• refactor AsyncMessageChannel code for browser implementation

• webpack use swc-loader for browser version + speed/bundle size plugin options

• prettify browser dev preview UI

• enable loading screen if startup params missing (for web serve + disconnected browser dev preview)

• attempt to fix webpack build for tests

• add SpeedMeasurePlugin package

• create AsyncMessageChannel dev docs

• replace web-preview.md ASCII data flow diagram with mermaid

• use radii/spacing tokens instead of px for web preview.tsx styles

• remove commented out startup handler (handled in startup.tsx useEffect now)

• remove commented out code

• replace px values with tokens

• conditional export for AsyncMessageChannel preview env

• add browser preview WEBSOCKETS_PORT env

• fix typescript issue with PreviewAsyncMessageChannel.isWsConnected

• add test coverage for AsyncMessageChannelPreview

• Browser preview debug UI (#2803)

• fix AsyncMessageChannelPreview undefined error + export WS URI

• browser preview CSS file for UI fixes

• create previewUtils for browser color scheme + setFigmaBrowserTheme

• browser preview URL params + fullscreen/theme/action modes

• two bug fixes for browser/plugin websocket preview bridge

• add preview dist folder for web preview builds

• [WIP] browser preview dev knowledge docs

• feat(dev): request startup on browser preview page open

• refactor(dev): use env vars for browser preview ws src

• fix(debug): remove console.log from asyncmessagechannelpreview

• fix(css): figmaloading full height css for browser preview

• refactor(dev): use enums for websockets src in browser preview tsx

• fix(dev): remove comments

• refactor: reuse htmlClassList variable

• remove unused package

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Why does this PR exist?

Closes #2748

What does this pull request do?

Testing this change

Additional Notes (if any)