add review-bot to require fellows as reviewers

.github/review-bot.yml

@@ -0,0 +1,32 @@
+rules:
+  - name: CI Files
+    condition:
+      include:
+        - ^\.github/.*
+    type: fellows
+    minRank: 4
+    minApprovals: 2
+  - name: Relay and system files
+    condition:
+      include:
+        - ^relay\/kusama\/.*
+        - ^relay\/polkadot\/.*
+        - ^system-parachains\/.*
+        - ^CHANGELOG$
+      exclude: 
+        - ^relay\/.+\.adoc$
+    type: fellows
+    minRank: 3
+    minApprovals: 4
+  - name: General Files
+    condition:
+      include:
+        - '.*'
+      exclude: 
+        - ^relay\/kusama\/.*
+        - ^relay\/polkadot\/.*
+        - ^\.github/.*
+        - ^system-parachains\/.*
+        - ^target\/.*
+    type: fellows
+    minRank: 2

.github/workflows/review-bot.yml

@@ -0,0 +1,32 @@
+name: Review PR
+on:
+  pull_request_target:
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - review_requested
+      - review_request_removed
+      - ready_for_review
+  pull_request_review:
+
+permissions:
+  contents: read
+  checks: write
+
+jobs:
+  review-approvals:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Generate token
+        id: team_token
+        uses: tibdex/github-app-token@v1
+        with:
+          app_id: ${{ secrets.REVIEW_APP_ID }}
+          private_key: ${{ secrets.REVIEW_APP_KEY }}
+      - name: "Evaluates PR reviews and assigns reviewers"
+        uses: paritytech/review-bot@v2.0.0
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          team-token: ${{ steps.team_token.outputs.token }}
+          checks-token: ${{ steps.team_token.outputs.token }}