Add github action for codespace

.github/workflows/codespaces.yaml

@@ -0,0 +1,19 @@
+name: prebuild codespace
+on:
+  push:
+    branches:
+    - master
+    - codespaces-sandbox
+  workflow_dispatch: 
+
+jobs:
+  createPrebuild:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: github/codespaces-precache@v1-stable
+      with:
+        regions: WestUs2 EastUs WestEurope SouthEastAsia
+        sku_name: premiumLinux
+      env:
+        GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}