Add sorbet for type checking

[Throne3d]

No idea if we'll ever merge this, just wanted to test out how it'd look + what it'd be like!

Update via:

• bundle exec tapioca init
• If we get new entries in sorbet/rbi/todo.rb, try adding entries to sorbet/tapioca/require.rb for those items, or if necessary create an entry in shims/gems.
• bundle exec tapioca generate (previously gems)
• bundle exec tapioca dsl
• bundle exec srb tc - check type checking

Shopify/tapioca#1266

[Throne3d]

There's a truly insane amount of vendored code here - TODO: gitignore sorbet/rbi (against the upstream recommendation) and just tell people to generate these files locally?