add mergeable.yaml

Author: waynz0r

.github/mergeable.yml

@@ -0,0 +1,20 @@
+version: 2
+mergeable:
+  - when: pull_request.*
+    validate:
+      - do: title
+        must_exclude:
+          regex: '^(\[wip\]|wip:)'
+          message: 'WIP tag in PR title'
+      - do: label
+        must_exclude:
+          regex: 'wip'
+          message: 'WIP label on PR'
+      - do: description
+        and:
+          - must_exclude:
+              regex: '\[ \]'
+              message: 'Remaining tasks in the description.'
+          - must_exclude:
+              regex: 'no\|yes|fixes #X, partially #Y, mentioned in #Z'
+              message: 'Please fill out the PR template.'