CI: Set up release workflow (#16)

Draft releases are automatically generated when tagging.

.github/workflows/release.yml

@@ -0,0 +1,52 @@
+on:
+  push:
+    tags:
+      - v*
+
+name: Release
+
+jobs:
+
+  release:
+    name: create a release
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v1
+        with:
+          node-version: '12.x'
+      - name: Determine release name
+        run: echo "::set-env name=RELEASE_FILENAME::reservation-web-${GITHUB_REF##*/}"
+      - run: npm install
+      - name: Build release bundle
+        run: |
+          cp .env.example .env && \
+          npm run build && \
+          mv public ${RELEASE_FILENAME} && \
+          tar cfvz ${RELEASE_FILENAME}.tar.gz ${RELEASE_FILENAME}
+      - name: Create release
+        id: create_release
+        uses: actions/create-release@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          tag_name: ${{ github.ref }}
+          release_name: Release ${{ github.ref }}
+          draft: true
+          prerelease: false
+          body: |
+            Release automatically generated by GitHub workflows.
+
+            NOTE: Because the env variables are processed at build time,
+            you need to replace the `PLEASE_SET_API_TOKEN_VARIABLE` string
+            in the release build with the actual API token.
+      - name: Upload release assets
+        id: upload_release_asset
+        uses: actions/upload-release-asset@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          upload_url: ${{ steps.create_release.outputs.upload_url }}
+          asset_path: ./${{ env.RELEASE_FILENAME }}.tar.gz
+          asset_name: ${{ env.RELEASE_FILENAME }}.tar.gz
+          asset_content_type: application/gzip