ci: add lint job

.github/workflows/firebase-hosting-pull-request.yml

@@ -8,9 +8,26 @@ permissions:
   contents: read
   pull-requests: write
 jobs:
+  lint:
+    if: ${{ github.event.pull_request.head.repo.full_name == github.repository }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: install nix
+        uses: DeterminateSystems/nix-installer-action@main
+      - name: load nix cache
+        uses: DeterminateSystems/magic-nix-cache-action@main
+
+      - name: run linters
+        run: nix develop --command just lint
+
   build_and_preview:
     if: ${{ github.event.pull_request.head.repo.full_name == github.repository }}
     runs-on: ubuntu-latest
+    needs:
+      # don't run if lint fails
+      - lint
     steps:
       - uses: actions/checkout@v4