feat: rewrite homepage with vitepress

[zoey-kaiser]

Closes #174

This PR:

• Migrates https://sidebase.io to a new Vitepress page, hosted via Github Pages
• Adds redirects from the previous NuxtAuth docs to the new docs found under https://auth.sidebase.io

Checklist:

• issue number linked above after pound (#)
  • replace "Closes " with "Contributes to" or other if this PR does not close the issue
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