Feat. Allowing the owner of the action to specify the nix version

Signed-off-by: Eoghan Conlon <eoghanconlon73@skynet.ie>

README.md

@@ -107,11 +107,13 @@ jobs:
 
 ## Docker Nix
 This action is used to get nix into the docker user deploy system.
-### vx
+### v7
 ```yaml
 jobs:
   build:
     runs-on: docker
     steps:
-      uses: https://forgejo.skynet.ie/Skynet/actions/docker_nix@vx
+      uses: https://forgejo.skynet.ie/Skynet/actions/docker_nix@v7
+      with:
+        nix_version: nixos-unstable
 ```

docker_nix/action.yml

@@ -3,7 +3,7 @@ description: 'Update apt repositories and installing sudo'
 runs:
   using: 'composite'
   steps:
-    - name: 'Get image ready to run nix jobs'
+    - name: 'Installing nix on Docker runner'
       shell: bash
       run: |
         apt update
@@ -11,7 +11,7 @@ runs:
         apt install sudo
     - uses: https://github.com/cachix/install-nix-action@v29
       with:
-        nix_path: nixpkgs=channel:nixos-unstable
+        nix_path: nixpkgs=channel:${{ inputs.nix_version }}
         extra_nix_config: |
           trusted-public-keys = skynet-cache:zMFLzcRZPhUpjXUy8SF8Cf7KGAZwo98SKrzeXvdWABo= hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
           substituters = https://nix-cache.skynet.ie/skynet-cache https://hydra.iohk.io https://cache.nixos.org/