Feature request: Add informational endpoint about snekbox

For those of us running our own snekbox instances, an informational endpoint would be useful. This could list the api version, the current version of snekbox, and perhaps the installed packages.

What kind of versioning would you like to see? Off the top of my head, the snekbox version could just be the commit hash and the API version could be something like semver.

That sounds good 👍