Link themes from external repositories

[belinhacbr]

Context:
As discussed in #halloy, the Catppuccin themes for Halloy have been updated to adhere to Catppuccin’s design guidelines and halloy's updated template. Currently, there’s duplication between:

• catppuccin/halloy

• squidowl/halloy-themes (used by themes.halloy.chat)

Goal:
Avoid maintaining separate versions by either:

• Syncing the themes (update halloy-themes with the latest Catppuccin versions), or

• Linking to catppuccin's halloy in the docs (if preferred by maintainers).

Suggested Action:

Converge both versions by adding support to halloy's theme library to link to an external file. Review the both Catppuccin themes for major differences.

[belinhacbr]

Happy to take this on since I started the discussion, please assign this issue to me. :)

[casperstorm]

Sounds good to me! Excited to see it come together.

[belinhacbr]

Thanks for merging so quickly @casperstorm ! Looking forward to seeing it live.

Following up to close the issue itself, these are the remaining next steps:

• Review Catppuccin all flavours available on catppuccin/halloy/squidowl/halloy-themes for major differences. Consolidate both versions
• Submit all Catppuccin flavours to themes.halloy.chat

[belinhacbr]

Thinking about it just now, I could also add a way to optionally refer to the original theme on Halloy's themes main view. Something like an external link arrow-like icon next to the preview button. That would require schema changes and the optional URL field on submit... 🤔 I'd love to hear your opinion on this, if it's a desirable feature or not.
Commenting here because it's related, would be another feature.