Add a GitHub action to manually trigger the generation of a release zip file

.github/workflows/build-release-zip-file.yml

@@ -0,0 +1,30 @@
+name: Build release zip file
+on:
+  workflow_dispatch:
+    inputs:
+      ref:
+        description: 'By default the zip file is generated from the branch the workflow runs from, but you can specify an explicit reference to use instead here (e.g. refs/tags/tag_name). The resulting file will be available as an artifact on the workflow run.'
+        required: false
+        default: ''
+jobs:
+  build:
+    name: Build release zip file
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+        with:
+          ref: ${{ github.event.inputs.ref || github.ref }}
+      - name: Build the zip file
+        id: build
+        uses: woocommerce/action-build@v2
+      - name: Unzip the file (prevents double zip problem)
+        run: unzip ${{ steps.build.outputs.zip_path }} -d zipfile
+      - name: Upload the zip file as an artifact
+        uses: actions/upload-artifact@v2
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          name: woocommerce
+          path: zipfile
+          retention-days: 7