gh: add pull request check

.github/workflows/build.yml

@@ -3,7 +3,6 @@ name: build
 on:
   push:
     branches: ["main"]
-  pull_request:
 
 jobs:
   build:

.github/workflows/pr.yml

@@ -0,0 +1,50 @@
+name: pr-check
+
+on:
+  pull_request:
+
+jobs:
+  fmt-check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+
+      - name: Check formatting
+        run: |
+          make fmt
+          git diff --exit-code || (echo "::error::Code is not formatted. Run 'make fmt' and commit the changes." && exit 1)
+
+  vet:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+
+      - name: Run go vet
+        run: go vet ./...
+
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+
+      - name: Run go test
+        run: go test ./...
+