Docusaurus migration

[JulienLavocat]

Description of Changes

• Migrate the documentation site to Docusaurus.
• Add a GitHub Action workflow that runs pnpm build on pull requests targeting master.
  This command checks for broken links and images and ensures the site builds correctly.
• Add a GitHub Action workflow to publish the docs automatically when a merge occurs on the docs/release branch.

Important: The workflows haven't been tested yet due to the fact that they need to be merged first before being able to run. It's a fairly basic workflow I don't expect this to block anyone but anyways I will make another PR with the complete changes when I can actually run it.

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API and ABI Breaking Changes

No breaking changes for SpacetimeDB users.
Documentation contributors should experience minimal disruption — content is still written in Markdown.

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Expected Complexity Level and Risk

Complexity: 3/5

Reasons:

1. Several adjustments were made to fit Docusaurus conventions:

   • Replaced our custom :::server-rust blocks with Docusaurus <Tabs/> components.
   • Converted “Note” callouts using admonitions instead of Markdown blockquotes.
   • Updated all images (including Unity tutorial ones, which were previously commented out).
   • Moved images from the DO bucket into the repository at docs/static/images.

2. Customized Docusaurus CSS and one component to apply our theme and color palette.

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Testing

Tested locally.

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Review Notes

This PR involves many file changes — a full code review is likely not productive.
Instead, please focus on verifying that the documentation content was migrated correctly:

• Review sections you’re familiar with to confirm accuracy.
• Ensure formatting, links, and images render as expected.

You can follow the updated README for instructions on running Docusaurus locally.

[jdetter]

One question on this one so far, otherwise the rest of the edits look good to me

[JasonAtClockwork]

I've reviewed the entire Unreal tutorial and it looks 100% (all links, code and images), the only thing is it looks like new version is missing the Unreal Reference from the Client SDK:

New:

Old:

[jdetter]

Reminder that I still needed to run this command in order to get the docs rendering:

pnpm add @docusaurus/theme-common

[jdetter]

I've reviewed a majority of the documentation and I think it looks good. There are just 2 issues to fix here I think:

1. Fix the issue with having to manually install @docusaurus/theme-common
2. Fix the code formatting issues in the Unity tutorial

besides that I think this is ready to go. Let me know when you want me to take another look 👍

[JulienLavocat]

the only thing is it looks like new version is missing the Unreal Reference from the Client SDK:
Added @JasonAtClockwork

[JasonAtClockwork]

the only thing is it looks like new version is missing the Unreal Reference from the Client SDK:
Added @JasonAtClockwork

Looks great! All the Unreal stuff is complete.

[jdetter]

Few more formatting issues here

[cloutiertyler]

This looks good enough to me now. I think we still need to do some updates on the styling, but I think we'll wait to do a full styling pass from Randy