Pkl LSP

This is an implementation of the Language Server Protocol for Pkl.

Features

✓ Diagnostics (WIP)
✓ Hover
✓ Go to definition
✓ Auto complete (WIP: definition level access still needed)
✓ Project syncing
✓ Package downloading
❏ Rename
❏ Find references
❏ Code lens
❏ Formatting
❏ Type checking
❏ Quick fixes