also add build status badge to README.md (very important)
---
Squashed commit of the following:
commit 226f181e6dded95357cf3e31c918e811bc6b9bae
Author: surtur <a_mirre@utb.cz>
Date: Wed May 4 16:37:08 2022 +0200
ci: add .drone.starlark
also add build status badge to README.md
* reformat the flake
* create a fyne application, specify deps as both buildGoModule
buildInputs and packages in devShells
* add nixGL overlay to devShells so that openGL-based apps (such as fyne
apps) run fine for non-NixOS users
* add build/link flags