[GoToSocial] Create guide

[thisven]

As Pleroma with PostgreSQL seems to be quite resource intensive for a single-user instance, I'd suggest GoToSocial. It's a lightweight, customizable, and safety-focused ActivityPub social network server without a web front-end written in Golang. Although it's currently in alpha stage, it seems to implement all crucial features and a beta release is planned this year according to the roadmap.