Add `overlays` to the flake outputs.
- the `default` `overlay` supplies the package with the `zellij` name
- the `nightly` `overlay` supplies the package with the `zellij-nightly` name
Build a musl package from the repo, by invoking:
```
nix build "github:zellij-org/zellij#zellij-musl"
```
makes it possible to build bundled applications, that don't need patches
to run:
```
nix bundle --bundler github:NixOS/bundlers#toDEB "github:zellij-org/zellij#zellij-musl"
```
This will build a `.deb` file, that can be installed with apt.
* add(ci): install `cargo-make` through `nix`
Should speed the e2e tests up by about 2 minutes.
Can easily reverted by `commenting/uncommenting`
the `run` part of the `Install cargo-make` step.
* check if cachix speeds the process up
* add(nix): add crate2nix
To have a better experience on ci, due to improved caching
of dependencies. Also organize file hierarchy slightly.
* ci(nix): manually check a default system
Is needed because `nix flake check` accidentally tries to build IFD.
