feat: add cross-compile and release pipeline

- Enhanced Makefile with cross-compilation for linux/amd64, linux/arm64,
  darwin/arm64, windows/amd64, windows/arm64
- Added GitHub Actions CI workflow for testing on all platforms
- Added GitHub Actions Release workflow triggered by version tags
- Added VERSION file for version tracking
- Added scripts/release.sh for automated release process
- Added Dockerfile for containerized builds
- Added CONTRIBUTING.md with release process documentation
- Added CHANGELOG.md for version tracking
- Updated .gitignore to exclude build artifacts
- Fixed unused variable in cmd/obm/main.go
- Version now injected via ldflags (main.version, main.gitCommit, main.buildTime)

.github/workflows/ci.yml

@@ -0,0 +1,84 @@
+name: CI
+
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+    branches: [main, master]
+
+jobs:
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.22'
+          cache: true
+
+      - name: Download dependencies
+        run: go mod download
+
+      - name: Run vet
+        run: make vet
+
+      - name: Run tests
+        run: make test
+
+      - name: Check formatting
+        run: |
+          if [ -n "$(gofmt -l -s .)" ]; then
+            echo "Files not properly formatted:"
+            gofmt -l -s .
+            exit 1
+          fi
+
+      - name: Build
+        run: make build
+
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    needs: test
+    strategy:
+      matrix:
+        goos: [linux, darwin, windows]
+        goarch: [amd64, arm64]
+        exclude:
+          # Exclude darwin/amd64 - Apple Silicon is the future
+          - goos: darwin
+            goarch: amd64
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.22'
+          cache: true
+
+      - name: Build binary
+        env:
+          GOOS: ${{ matrix.goos }}
+          GOARCH: ${{ matrix.goarch }}
+          CGO_ENABLED: 0
+        run: |
+          VERSION=$(cat VERSION)
+          BINARY_NAME="obm"
+          if [ "$GOOS" = "windows" ]; then
+            BINARY_NAME="obm.exe"
+          fi
+          LDFLAGS="-s -w -X main.version=$VERSION"
+          GOOS=$GOOS GOARCH=$GOARCH go build -ldflags "$LDFLAGS" -o "bin/${GOOS}_${GOARCH}/$BINARY_NAME" ./cmd/obm
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: obm-${{ matrix.goos }}-${{ matrix.goarch }}
+          path: bin/${{ matrix.goos }}_${{ matrix.goarch }}/
+          retention-days: 7