CI: run shellcheck

.github/workflows/shellcheck.yml

@@ -0,0 +1,32 @@
+name: Shellcheck
+
+on:
+  pull_request:
+  push:
+    branches:
+      - smelc/release-create-changelog
+
+jobs:
+  example:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Nix with good defaults
+        uses: input-output-hk/install-nix-action@v20
+        with:
+          extra_nix_config: |
+            trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=
+            substituters = https://cache.iog.io/ https://cache.nixos.org/
+          nix_path: nixpkgs=channel:nixos-unstable
+      - uses: cachix/install-nix-action@v18
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+      # To make the environment in your flake's devShell available to future
+      # steps:
+      - uses: rrbutani/use-nix-shell-action@v1
+        with:
+          devShell: .#default # this is the default
+      - name: Shellcheck
+        run: |
+          # We want expansion
+          # shellcheck disable=SC2046
+          shellcheck $(git ls-files "*.hs")