Document the default behavior when --watch flag is not present

[jhrcek]

Describe the feature you’d like to be implemented

It would be nice to mention (maybe in --help, but definitely in docs) what exactly is being watched when --watch flag is not specified.

Is cabal file included in the watching by default? It seems to me that there are no reloads on cabal file changes (in which case this is a bug report). Is it all .hs files found in current directory?

List alternatives to the feature and their pros and cons

No response

Additional context

Thank you for opensourcing this great tool, I switched my project to it from ghcid and I'm excited it fixes many issues that I had with ghcid