Deprecate this plugin

[nilsnolde]

I'm planning to move away from this plugin for our blog and instead go with mkdocs and deploying it via Github Actions, which I recently did for Valhalla and the experience super pleasant. That'll also be a bit less maintenance hassle and with all the open-source projects & open infrastructures I'm currently maintaining, any single bit less (literally) is very welcome.

Some people might depend on this plugin, even if it's likely just a few users. It also will surely run for a while to come without any modifications, but I didn't even get around to test WordPress v6.x yet. I created this plugin solely for our own purposes and open sourced it out of ideology. I learned though that it's not a good idea to attempt to maintain something that is of no use to oneself. And that will soon be the case.

So if anyone feels like this is valuable enough to preserve and wants to maintain it, I'm happy to transfer the repo. If not, I won't have a problem deprecating it either. Cc @danilopinotti @LuigiBella, in fact you're the only ones I know for sure, who at least used to use this plugin, so just letting you know explicitly:)