[docs] Cut branch 0.86

[fabriziocucci]

Summary

Publishes the 0.86 documentation version.

• Adds 0.86 to versions.json so it appears in the version selector and becomes the default docs version
• Refreshes the version-0.86 versioned docs and sidebar via yarn version:cut 0.86

Follows up on #5071 ([docs] Cut version 0.86 (unpublished)), which created the snapshot without publishing it.

Test plan

• yarn build succeeds
• Version selector on /docs/getting-started lists 0.86 as the latest version

[Simek]

IIRC the idea to cut 0.86 early was to be able to update next docs with changes for 0.87, so probably we should not re-cut it again, CC @huntie.

[huntie]

@Simek Oh wait, YEAH! — Note is on #5071. This commit's changes overwrite.

@fabriziocucci Can we revert and instead enable "0.86" here: facebook/react-native-website@main/website/versions.json.

[huntie]

Let's squash and merge ✅