meta: convert workflow file to GitHub Actions v2 yml syntax

.github/workflows/pull_request_triage.yml

@@ -0,0 +1,14 @@
+on: pull_request
+name: Triage Pull Request
+jobs:
+  mainJob:
+    name: Triage
+    if: github.event.action == 'opened' || github.event.action == 'synchronize'
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@master
+    - name: Analyze and triage
+      uses: ohmyzsh/github-actions/pull-request-triage@master
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}