test stuff when you don't have a clue how to install swift
I could have [helped](https://swift.org/download/#using-downloads "Swift.org") with that.
After that, you may actually use [`filetype_extensions.conf`](https://raw.githubusercontent.com/ankitpati/geany/2a86cad6f3219e02a967a357da... "PR 1323") and [`filetypes.Swift.conf`](https://raw.githubusercontent.com/ankitpati/geany/2a86cad6f3219e02a967a357da... "PR 1323") from this very PR to get Swift support in Geany.