readded asset manifests

[perriDplatypus]

Reactivated assets/manifest.json (ISSUE #47)

[sweep-ai]

Apply Sweep Rules to your PR?

• Apply: All new business logic should have corresponding unit tests.
• Apply: Refactor large functions to be more modular.
• Apply: Add docstrings to all functions and file headers.

[martindale]

The manifest should be built with the latest information from Compiler, which provides the webpack configuration — ideally, the build file includes some hash which changes on every build, which regenerates manifest.json