.github: add labeler action (#15189)

.github/CODEOWNERS

@@ -1,6 +1,7 @@
 /distsql @pingcap/co-exec
 /executor @pingcap/co-exec
-/exec @pingcap/co-exec
+/expression @pingcap/co-exec
+/types @pingcap/co-exec
 /util/chunk @pingcap/co-exec
 /util/disk @pingcap/co-exec
 /util/execdetails @pingcap/co-exec

.github/labeler.yml

@@ -0,0 +1,28 @@
+component/executor:
+  - distsql
+  - executor
+  - util/chunk
+  - util/disk
+  - util/execdetails
+  - util/expensivequery
+  - util/filesort
+  - util/memory
+  - util/sqlexec
+
+component/expression:
+  - expression
+  - types
+
+component/planner:
+  - planner
+  - bindinfo
+  - util/ranger
+  - util/plancodec
+
+component/statistics:
+  - statistics
+
+component/DDL:
+  - ddl
+  - infoschema
+  - meta

.github/workflows/labeler.yml

@@ -0,0 +1,11 @@
+name: "Pull Request Labeler"
+on:
+- pull_request
+
+jobs:
+  triage:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/labeler@v2
+      with:
+        repo-token: "${{ secrets.GITHUB_TOKEN }}"