Add task mirroring devops release branch artifact building pipeline

.github/workflows/release-branch-artifact.yaml

@@ -0,0 +1,47 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - release-*
+  pull_request:
+    branches:
+      - release-*
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Use node version 12
+      uses: actions/setup-node@v1
+      with:
+        node-version: 12
+    - name: Remove existing TypeScript
+      run: |
+        npm uninstall typescript --no-save
+        npm uninstall tslint --no-save
+    - name: npm install and test
+      run: |
+        npm install
+        npm update
+        npm test
+      env:
+        CI: true
+    - name: Validate the browser can import TypeScript
+      run: gulp test-browser-integration
+    - name: LKG, clean, and pack
+      run: |
+        gulp LKG
+        gulp clean
+        npm pack ./
+        mv typescript-*.tgz typescript.tgz
+      env:
+        CI: true
+    - name: Upload built tarfile
+      uses: actions/upload-artifact@v1
+      with:
+        name: tgz
+        path: typescript.tgz
+