Add new regex example to --exclude docs

[Nickedude]

Description

Fixes #10250

Adds an example on how to use the OR-operator to combine two regular expressions in order to ignore multiple file or directory names.

[emmatyping]

I think in #10250 @JukkaL wanted multiple examples of how to use --exclude, but this is definitely an improvement and a longer set of examples can be done in a separate PR. (But we should make sure #10250 stays open)

[hauntsaninja]

@ethanhs I left #10250 open, but I'm curious what examples you'd like to see. The current docs have examples for files, directories, subpaths and now OR combination.

For the question of allowing passing exclude multiple times / allowing it to be a list, let's use #10310

[emmatyping]

@hauntsaninja I was referring to #10250 (comment)