ci: add golangci-lint and gofumpt workflows

Author: nnemirovsky

.github/workflows/lint.yml

@@ -0,0 +1,46 @@
+name: Lint
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  golangci-lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+
+      - uses: golangci/golangci-lint-action@v7
+        with:
+          version: v2.9.0
+
+  gofumpt:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+
+      - name: Install gofumpt
+        run: go install mvdan.cc/gofumpt@latest
+
+      - name: Check formatting
+        run: |
+          unformatted=$(gofumpt -l .)
+          if [ -n "$unformatted" ]; then
+            echo "Files not formatted with gofumpt:"
+            echo "$unformatted"
+            echo ""
+            echo "Run 'gofumpt -w .' to fix."
+            exit 1
+          fi