chore: automatically add label

.github/labeler.yml

@@ -0,0 +1,5 @@
+playground:
+  - playground/**/*
+
+translation:
+  - src/_data/sites/*

.github/workflows/label.yml

@@ -0,0 +1,21 @@
+# This workflow will triage pull requests and apply a label based on the
+# paths that are modified in the pull request.
+#
+# To use this workflow, you will need to set up a .github/labeler.yml
+# file with configuration.  For more information, see:
+# https://github.com/actions/labeler
+
+name: Labeler
+on: [pull_request_target]
+
+jobs:
+  label:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
+
+    steps:
+      - uses: actions/labeler@v2
+        with:
+          repo-token: "${{ secrets.GITHUB_TOKEN }}"