Add file-based automated PR labeling

Signed-off-by: Bryan Richter <b@chreekat.net>

Author: chreekat

.github/labeler.yml

@@ -0,0 +1,57 @@
+bazel:
+  - changed-files:
+      - any-glob-to-any-file:
+          - BUILD.bazel
+          - MODULE.bazel
+          - WORKSPACE.bzlmod
+          - .bazelrc
+          - .bazelversion
+          - '**/BUILD.bazel'
+          - 'bazel/**'
+
+protobuf:
+  - changed-files:
+      - any-glob-to-any-file:
+          - 'proto/**'
+
+specification:
+  - changed-files:
+      - any-glob-to-any-file:
+          - 'docs/**'
+
+python:
+  - changed-files:
+      - any-glob-to-any-file:
+          - 'py/**'
+
+rust:
+  - changed-files:
+      - any-glob-to-any-file:
+          - 'rust/**'
+
+go:
+  - changed-files:
+      - any-glob-to-any-file:
+          - 'go/**'
+
+codegen:
+  - changed-files:
+      - any-glob-to-any-file:
+          - 'codegen/**'
+
+dependencies:
+  - changed-files:
+      - any-glob-to-any-file:
+          - .gitmodules
+          - .github/dependabot.yml
+
+github_actions:
+  - changed-files:
+      - any-glob-to-any-file:
+          - '.github/workflows/**'
+          - '.github/actions/**'
+
+documentation:
+  - changed-files:
+      - any-glob-to-any-file:
+          - '*.md'

.github/workflows/labeler.yml

@@ -0,0 +1,15 @@
+name: Labeler
+
+on:
+  pull_request_target:
+    types: [opened, synchronize]
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  label:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/labeler@v5