Add community resources section to README

[jo-chemla]

Added a section for community resources and integrations related to 3DTilesRendererJS.

See context at #1576 (comment)

[sguimmara]

@jo-chemla Thanks for adding Giro3D to the list !

[gkjohnson]

This section is a bit hard to read and visually parse with so many links. I don't think it will be clear to readers what is intended to be communicated or what the link is that they're clicking on:

I think we should relegate these to a single link per line and then a description after if needed. Likewise we should be linking to long lived links and not anything like PRs that will become closed or outdated, which would then require maintenance. Something like so:

• 3D Tiles in MapLibre Guide: Official example showing how to render 3D tiles using a synced Three.js layer.

[jo-chemla]

This looks nicer indeed after a second pass, thanks for the feedback! I usually used the projects official taglines from repo or doc, with slight rewording for consistency.

[gkjohnson]

Thanks!