Add support for specific files for tracking

[polRk]

Example: `--watch="./build/*"

Now to many rerenders

[mrbbot]

Hey! 👋 Apologies for the delayed response. I've recently returned from a long holiday and am just starting to catch up on issues now.

By default, Miniflare will only watch your worker script, and configuration files. If you'd like to trigger a custom build when other files change, you should be able to use the --build-watch-path flag. This should update your worker script.

Does this cover your use case? Let me know if I'm missing something.