No such thing currently exists within Lemmy. It isn't a big deal to make a new community and do whatever you want with it. Or if all you want is a single post you could make a wiki community and set it to moderators only posting and then curate posts yourself as requested.
There is currently no /c/wiki community so it is free for the taking.
I bet there are services you can use to host a wiki, after that you can add a link to the description of the community. Seems a reasonable workaround, it will be quite confusing for a bit until enough people do it that a straightforward approach is adopted by most servers.