For the AMP runtime, we enforce JSDoc requirements for all code, and check types using closure compiler. However, build-system/ currently lacks JSDoc enforcement, and we do not type-check it using closure.

This issue is to track two things:

• Enforce JSDoc requirements and backfill missing documentation for existing code.
• Do some sort of type checking. If not closure, perhaps use typescript? Or failing that, maybe there's an eslint plugin that can do it?