add build workflow

.github/workflows/main.yml

@@ -0,0 +1,56 @@
+name: CI
+
+on:
+  push:
+    tags:
+    - 'v*'
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Get the version (git tag)
+      id: get_version
+      run: |
+        echo ${GITHUB_REF/refs\/tags\//}
+        echo ::set-output name=VERSION::${GITHUB_REF/refs\/tags\//}
+    - name: Build Image
+      run: |
+        docker build -t boot2homebridge .
+        docker run --rm boot2homebridge > boot2homebridge.iso
+    - name: Calculate Checksum
+      id: get_sha256_checksum
+      run: |
+        export IMAGE_SHA256_CHECKSUM=$(shasum -a 256 boot2homebridge.iso | awk '{print $1}')
+        echo "$IMAGE_SHA256_CHECKSUM boot2homebridge.iso"
+        echo ::set-output name=IMAGE_SHA256_CHECKSUM::${IMAGE_SHA256_CHECKSUM}
+    - name: Create Release
+      id: create_release
+      uses: actions/create-release@v1
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      with:
+        tag_name: ${{ github.ref }}
+        release_name: ${{ github.ref }}
+        body: |
+          Click the link below to start your download:
+          <span align="center">
+          ### [boot2homebridge.iso](https://github.com/oznu/boot2docker/releases/download/${{ steps.get_version.outputs.VERSION }}/boot2homebridge.iso)
+          </span>
+          ---
+          * **SHA-256:** ${{ steps.get_sha256_checksum.outputs.IMAGE_SHA256_CHECKSUM }}
+        draft: false
+        prerelease: true
+    - name: Upload Image
+      id: upload-release-asset 
+      uses: actions/upload-release-asset@v1
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      with:
+        upload_url: ${{ steps.create_release.outputs.upload_url }}
+        asset_path: boot2homebridge.iso
+        asset_name: boot2homebridge.iso
+        asset_content_type: application/x-iso9660-image