add auto assign bot

.github/auto_assign.yml

@@ -1,3 +1,3 @@
 addReviewers: true
 reviewers: [/mtfwiki-editors]
-numberOfReviewers: 1
+numberOfReviewers: 0

.github/workflows/auto-assign.yml

@@ -0,0 +1,11 @@
+name: Auto Assign
+
+on:
+  pull_request:
+    types: [opened, ready_for_review]
+
+jobs:
+  add-reviews:
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: kentaro-m/auto-assign-action@v1.2.5

.github/workflows/labeler.yml

@@ -8,6 +8,6 @@ jobs:
     permissions:
       contents: read
       pull-requests: write
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/labeler@v4