Add sync-labels action

.github/labels.yaml

@@ -0,0 +1,40 @@
+# Warning
+- color: "ee0701"
+  description: "Categorize bug reports."
+  name: ":warning: bug"
+- color: "ee0701"
+  description: "Categorize vulnerability reports."
+  name: ":warning: vulnerability"
+
+# Highlight
+- color: "0e8a16"
+  description: "Good for newcomers."
+  name: ":fire: good first issue"
+- color: "0e8a16"
+  description: "Extra attention is needed."
+  name: ":fire: help wanted"
+
+# Cancel
+- color: "b60205"
+  description: "This issue or pull request already exists."
+  name: ":pray: duplicate"
+- color: "b60205"
+  description: "This will not be worked on."
+  name: ":pray: wontfix"
+
+# Size
+- color: "cfd3d7"
+  description: "Extra Small size issue or PR."
+  name: "size/XS"
+- color: "cfd3d7"
+  description: "Small size issue or PR."
+  name: "size/S"
+- color: "cfd3d7"
+  description: "Medium size issue or PR."
+  name: "size/M"
+- color: "cfd3d7"
+  description: "Large size issue or PR."
+  name: "size/L"
+- color: "cfd3d7"
+  description: "Extra Large size issue or PR."
+  name: "size/XL"

.github/workflows/sync-labels.yaml

@@ -0,0 +1,25 @@
+name: Sync labels
+
+on:
+  push:
+    branches:
+    - master
+    paths:
+    - .github/labels.yaml
+
+jobs:
+  sync-labels:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+
+    - name: Sync labels
+      uses: crazy-max/ghaction-github-labeler@v3
+      with:
+        github-token: ${{ secrets.GITHUB_TOKEN }}
+        yaml-file: .github/labels.yaml
+        skip-delete: false
+        dry-run: false
+        # exclude: |