Docs missing an example of adding multiple regexp for the same mode

[jasonhemann]

Right now the docs for the :mode keyword show how to add a single regexp to the auto-word-alist but don't show how to add multiple regexps.

1. I could imagine wanting to add with a single :mode keyword arg several different regexps that all should be added to a single mode.
2. I could imagine wanting a shorthand, say, if the package name is the name of the mode, I should still get to succinctly list the regular expressions.
3. I think I could imagine a given package defining two modes, so that two different regular expressions would match two different modes, and you'd want to/need to specify which mode goes with which regexp.

At least at present, I can't find any of those examples listed in the :mode documentation.