ci: fix add nix develop

Author: robjtede

.github/workflows/ci.yml

@@ -45,6 +45,9 @@ jobs:
         with:
           toolchain: ${{ matrix.toolchain.version }}
 
+      - name: Enter Nix Devshell
+        uses: nicknovitski/[email protected]
+
       - name: Workaround MSRV issues
         if: matrix.toolchain.name == 'msrv'
         run: just downgrade-for-msrv