Prototype: Automatic PR Labeler (#27015)

* prototype: automatic labeler

* fix?

* fix?

.github/labeler.yml

@@ -0,0 +1,15 @@
+lang/core:
+- src/core/**
+- include/core/**
+- test/core/**
+- tools/codegen/core/**
+
+lang/c++:
+- src/cpp/**
+- include/grpc++/**
+- include/grpcpp/**
+- test/cpp/**
+
+area/infra:
+- .github/**
+

.github/workflows/pr-auto-tag.yaml

@@ -0,0 +1,12 @@
+name: PR AutoTag
+on:
+  pull_request_target:
+    types: [opened, reopened, synchronized, edited]
+jobs:
+  triage:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/labeler@v3
+      with:
+        repo-token: "${{ secrets.GITHUB_TOKEN }}"
+