Add rule for typechecking maintainers (#161307)

Allow the following people merge rights on type checking configs:
  - @lolpack
  - @maggiemoss
  - @ndmitchell
  - @kinto0

Pull Request resolved: https://github.com/pytorch/pytorch/pull/161307
Approved by: https://github.com/albanD, https://github.com/ezyang

.github/merge_rules.yaml

@@ -525,6 +525,21 @@
   - Lint
   - pull
 
+- name: typechecking
+  patterns:
+  - 'pyrefly.toml'
+  - 'mypy.ini'
+  - 'mypy-strict.ini'
+  approved_by:
+  - lolpack
+  - maggiemoss
+  - ndmitchell
+  - kinto0
+  mandatory_checks_name:
+  - EasyCLA
+  - Lint
+  - pull
+
 - name: superuser
   patterns:
   - '*'