Build-in ZeroTier, add arm64 support, and simplify /app

🚀 Add ZeroTier, arm64 support, and some QOL fixes

- Adds ZeroTier support within the container (currently not toggleable).
- Add arm64 support.
- Removes the need for a configuration file.
- Migrates Corefile into /app, as it's now more generic (while still
  supporting same name-resolution features).
- Move to port 5053 exposure so that it doesn't conflict with built-in
  DNS services.
- Move from hand-built ZeroTier API to ZTC, a project by one of
  ZeroTier's founders to access ZeroTier Central's API.
  - TODO: figure out how to lessen the bloat from node.js app.
- Migrate from `invoke` to `click` for CLI interface.