Migrate Github Actions to YAML format

Author: mheap

.github/main.workflow

@@ -0,0 +1,21 @@
+name: Push to Master
+on:
+  push:
+    branches:
+      - master
+jobs:
+  build:
+    name: Update NDP Submodule
+    runs-on: ubuntu-latest
+    steps:
+    - name: Update NDP Submodule
+      uses: nexmo/github-actions/submodule-auto-pr@master
+      env:
+        GH_ADMIN_TOKEN: ${{ secrets.GH_ADMIN_TOKEN }}
+        PR_ACTIVE_BRANCH: master
+        PR_BRANCH_NAME: automated-python-snippets-update
+        PR_SUBMODULE_PATH: .repos/nexmo/nexmo-python-code-snippets
+        PR_TARGET_BRANCH: master
+        PR_TARGET_ORG: nexmo
+        PR_TARGET_REPO: nexmo-developer
+        PR_TITLE: nexmo-python-code-snippets Update