Provide a gitignore template

Hello, and thank you very much for this little alternative to storybook. There are not that many, and I'm glad that this one exists. It's been a while since I use Astro, and I'm trying to use Astrobook inside an existing project which is not Astro-based. I got a `.astro` folder containing a lot of files, and I was wondering if it's safe to add that to gitignore. If that is the case, maybe that can be documented or added as a template when explaining how to set up Astrobook. Thanks!