New:
- Turn on `filsystem` cache by default in webpack 5
- An `addBuildDependencies` plugin API for plugins to add additional
dependencies to the cache config

To Fix:
- Need to implement a `--no-cache` option for both `serve` and `build`
command
- Need to decide how to deal with `.js` config files when a random
environment variable change may affect its exports
- `lintOnSave` option needs an overhaul to work better with webpack 5
and the new cache mechanism
- Not sure how to test the cache implementation