Strawman: Unify writing style of action arguments

[shyndman]

This started off as documenting the exclude_patterns parameter (urlstechie/urlchecker-python#60), but I decided to take a stab at writing the param descriptions with a more consistent style.

I'm not attached to anything. Please feel free to criticize or suggest alternatives.

If accepted, I'll update the rest of this project (actions.yml, the examples, etc.), and https://github.com/urlstechie/urlchecker-python, to reflect the decisions.

[vsoch]

These changes look great to me - much more succinct and clear. If you'd like to add more to this PR, I'd be happy to review again (and ping me when ready) or we can split into separate PRs.

And I'm wondering if it makes sense to switch the default branch from master to main (another PR of course) since it will be main as default on GitHub from here on out (and many of my default branches I've changed to main).

[shyndman]

Excellent. Will do.

And I'm wondering if it makes sense to switch the default branch from master to main (another PR of course) since it will be main as default on GitHub from here on out (and many of my default branches I've changed to main).

sgtm