Add PR labeler based on LoC (#50)

* Add PR labeler based on LoC

* Update LoC label names

* Move labeler as a standalone workflow triggerd by pull_request_target

.github/configs/labeler.yml

@@ -0,0 +1,20 @@
+version: 1
+labels:
+  - label: "size/XS"
+    size-below: 10
+  - label: "size/S"
+    size-above: 9
+    size-below: 30
+  - label: "size/M"
+    size-above: 29
+    size-below: 100
+  - label: "size/L"
+    size-above: 99
+    size-below: 500
+  - label: "size/XL"
+    size-above: 499
+    size-below: 1000
+  - label: "size/XXL"
+    size-above: 999
+  - label: "testing-needed-e2e-fast"
+    size-above: 99

.github/workflows/labeler.yml

@@ -0,0 +1,20 @@
+name: "Pull Request Labeler"
+on:
+- pull_request_target
+
+jobs:
+  triage:
+    permissions:
+      contents: read
+      pull-requests: write
+    runs-on: ubuntu-latest
+    steps:
+    # Source: https://github.com/srvaroa/labeler
+    # Using this instead of the GH labeler action as the former supports labeling based on LoC changed.
+    # However, it doesn't work with regex pattern to ignore generated files (CRDs, docs, etc.) in diff.
+    # An issue has been filed https://github.com/srvaroa/labeler/issues/33 to track this improvement.
+    - uses: srvaroa/labeler@v0.9
+      with:
+        config_path: .github/configs/labeler.yml
+      env:
+        GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"