Add auto-PR to update the submodule in NDP

Author: mheap

.github/main.workflow

@@ -0,0 +1,19 @@
+workflow "Commit Push" {
+  on = "push"
+  resolves = ["nexmo/github-actions/submodule-auto-pr@master"]
+}
+
+action "nexmo/github-actions/submodule-auto-pr@master" {
+  uses = "nexmo/github-actions/submodule-auto-pr@master"
+  secrets = ["GH_ADMIN_TOKEN"]
+  env = {
+    PR_TARGET_ORG = "nexmo"
+    PR_TARGET_REPO = "nexmo-developer"
+    PR_SUBMODULE_PATH = ".repos/nexmo/nexmo-python-code-snippets"
+    PR_BRANCH_NAME = "automated-python-snippets-update"
+    PR_TITLE = "nexmo-python-code-snippets Update"
+    PR_TARGET_BRANCH = "master"
+    PR_ACTIVE_BRANCH = "master"
+  }
+}
+