Support to Exclude Files in `leptosfmt.toml`

[LeoBorai]

Hi @bram209! Thank you so much for such a great tool in the Leptos ecosystem!

Im trying leptosfmt out and I found the need of excluding some files from running the formatter.

Im running leptosfmt like:

leptosfmt ./src

I have tried -x/--exclude but ends up being verbose, I was thinking that it could be handy to either:

a. Have a .leptosfmtignore file
b. Have exclude entry in leptosfmt.toml

This way we could provide list of paths to ignore if encountered by the glob pattern provided as INPUT_PATTERN.

Thanks again!