Update CONTRIBUTING.md

Author: yvan-sraka

CONTRIBUTING.md

@@ -16,11 +16,11 @@ cabal build --project-file=cabal.project.release cabal
 ```
 
 > **Note**
-> If you use Nix, it might be convenient to work in a shell that contains all `Cabal` development dependencies:
+> If you're using Nix, you might find it convenient to work within a shell that has all the `Cabal` development dependencies:
 > ```
 > $ nix-shell -p cabal-install ghc ghcid haskellPackages.fourmolu_0_12_0_0 pkgconfig zlib.dev
 > ```
-> This also provided, with only community support, by `nix develop github:yvan-sraka/cabal.nix`.
+> A Nix flake developer shell with these dependencies is also available, supported solely by the community, through the command `nix develop github:yvan-sraka/cabal.nix`.
 
 The location of your build products will vary depending on which version of
 cabal-install you use to build; see the documentation section