Exclude files based on file header and directory. (ex.: Auto generated)

[t4m45]

If possible, please add an option to exclude files based on their header.
Multiple auto generated files have either an <auto-generated /> tag or just a simple // auto generated comment.

I use LinqConnect which generated over 200 .cs files for me, so excluding them by extension would not work.

Also excluding a whole directory would come in handy as well.

In the .formatconfig it could look like this:

[*]
enable = true
allowed_extensions =
denied_extensions = .js .html .editorconfig
# new settings
denied_directories = lib res externals/helpers
denied_headers = auto-generated

Using this, if there were multiple helpers directories, only the one thats placed in an externals directory would be excluded.
You could use the format externals\\helpers instead of externals/helpers if you want to.

The extension should read the file's first, or first x lines and look for the strings set in the denied_headers field, and if any of them are found, the formatting should be cancelled.

[mynkow]

@t4m45 there is a PR similar to your request. Would you mind if you take a quick look and tell us what do you think?

#62