Drone release main (ref #1556) (#1557)

Drone release main (ref #1556) (#1557)

* publish docker images from main

* try with separate step

* redo, lots of boilerplate

* try to fix syntax

* unique step names

* fix docker tags, remove cargo-chef

* only build dev image on main branch

* use `ref` for condition, as `branch` uses the target branch for PRs

* consistent indents

* fix tag

* use lemmy-ui:dev image for `docker/dev` and `docker/federation`