Consider adding with-simulated-input package to testing section

[DarwinAwardWinner]

Hi, I have a package that you might want to include in the handbook. It's called with-simulated-input, and its purpose is to enable automated non-interactive testing of interactive commands. I use it extensively in the test suite for my other package, ido-completing-read+, which is heavily focused on user interaction.

[alphapapa]

Thanks for the suggestion. I've been meaning to try using that for testing helm-org-rifle, but I haven't gotten around to it. There are a few other testing tools in the Tasks section that I also need to add.