Add bootstrap builder workflow

.github/workflows/build-bootstrap.yml

@@ -0,0 +1,28 @@
+# workflow name
+name: Build bootstraps
+
+# on events
+on: [release]
+
+# workflow tasks
+jobs:
+  generate:
+    name: Generate cross-platform bootstrap builds
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout the repository
+        uses: actions/checkout@v2
+      - name: Get the version
+        id: get_version
+        run: echo ::set-output name=VERSION::$(echo $GITHUB_REF | cut -d / -f 3)
+      - name: Build bootstraps
+        run: |
+          cd bootstrap-builder && ./build_bootstrap.sh
+
+      - name: Release
+        uses: softprops/action-gh-release@v1
+        if: startsWith(github.ref, 'refs/tags/')
+        with:
+          files: bootstrap-builder/*.zip
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}