This way we can build node or the library locally using:
```sh
nix build
nix build .#node
nix build .#library
```
Or just start a shell with Go `1.19.x` using:
```
nix develop
```
Which simply has the same environment as the build shell for the node.
One known snag is that there is currently no simple way to keep `vendorSha256`
updated to match the contents of `go.mod` and `go.sum`. For more details see:
https://discourse.nixos.org/t/how-should-i-build-a-go-package-from-local-source/19490/8
One way around this would be to have our own `vendor` folder, but that's
also a pretty ugly solution that requires manual updating.
Resolves:
https://github.com/waku-org/go-waku/issues/256
Signed-off-by: Jakub Sokołowski <jakub@status.im>
