[enh] #162: Add mypy pre-commit hook

isort before black otherwise there is a conflict

.pre-commit-config.yaml

@@ -3,3 +3,7 @@ repos:
     rev: 21.5b0
     hooks:
     - id: black
+-   repo: https://github.com/pre-commit/mirrors-mypy
+    rev: v0.812
+    hooks:
+    - id: mypy