Implement --force

[DavisVaughan]

Branched from #476, this is a follow up to that PR to add back a way to --force formatting on command line provided files and folders, regardless of exclusion patterns and inclusion patterns

# Formats cpp11.R even though it matches an `default-exclude`
air format cpp11.R --force

# Formats r-code.txt even though it does not match a `default-include`
air format r-code.txt --force

# Recursively format all files (regardless of file type) in folder/, regardless of exclusions and inclusions
# (dangerous!)
air format folder/ --force 

With this PR, the "unsafe" thing becomes opt in, which feels right.

---

Note that --force only applies to exclude, default-exclude, and our internal default-include patterns. It does not apply to our .gitignore support because that's already a little complicated. We unconditionally respect your .gitignore, but due to the way the ignore Rust crate works, if you do air format git-ignored.R then it will format that regardless because the ignore crate author thinks that a user supplied file should always count, regardless of the .gitignore. I think that is much less of an issue compared to #476, because pre-commit knows to never call hooks on gitignored files, and it seems very unlikely that RStudio would ever do this. I'm not super worried about this, especially since we don't expose any way to turn off gitignore support anyways.

[lionel-]

Probably worth calling out the gitignore behaviour in the clap doc. I mostly use the LSP, but if I was a CLI user it'd affect me because I have gitignored folders containing scratch R files in my R projects.