Add labeler action (#3671)

👷 add labeler action

.github/labeler.yml

@@ -0,0 +1,38 @@
+version: 1
+
+labels:
+- label: "documentation"
+  files:
+    - "README.md"
+
+- label: "documentation"
+  files:
+    - "docs/.*"
+
+- label: "tests"
+  files:
+    - "tests/.*"
+
+- label: "CMake"
+  files:
+    - ".*CMakeLists.txt"
+
+- label: "CMake"
+  files:
+    - "cmake/.*"
+
+- label: "CI"
+  files:
+    - "github/workflows/.*"
+
+- label: "CI"
+  files:
+    - "github/external_ci/.*"
+
+- label: "S"
+  size-below: 10
+- label: "M"
+  size-above: 9
+  size-below: 100
+- label: "L"
+  size-above: 100

.github/workflows/labeler.yml

@@ -0,0 +1,14 @@
+name: "Pull Request Labeler"
+
+on:
+  - pull_request
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: srvaroa/labeler@master
+        env:
+          GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"