PLACEHOLDER: Move icon packs to the server

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Context

• Icons take a good chunk of the extension size, build time, build complexity
• These packs are generally only loaded to make them available to the user

Suggestion

• Move the icons out of the extension bundle so that they can be loaded remotely as needed

Requirements

• We probably still need to bundle a list of available icons
• We cannot just move the icons to the app as that would result into a circular dependency

Proposed solution

• Create dedicated GitHub repo and npm package so that it can be managed independently
• Import package locally exclusively for the list
  • SVGs could also be included in the package for direct usage by us, rather than the user
• Structure package so that each icon is available as SVG at dedicated address (no "import all" endpoint): /bootstrap/box.svg
• Deploy on Google Pages or Vercel but use our own domain, like icons.pixiebrix.com

Additional changes

• The AsyncIcon component should also be updated to avoid defaulting to the box icon while the icon loads, to avoid flicker
• It would be cool to create a mini reference html page where ALL the icons are visible and filterable

Related

• This issue replaces https://github.com/pixiebrix/pixiebrix-extension/issues/2019

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I'm available to discuss and pick this up when it becomes a higher priority.

[fregante]

Fixed by #5865