Add toml typing stubs

Fix typing errors with new version of mypy

pyproject.toml

@@ -48,8 +48,8 @@ bandit = "^1.6.2"
 black = {version = "^21.12b0", allow-prereleases = true, python = "^3.7"}
 blacken-docs = "^1.8.0"
 ipython = { version = "^7.18.1", python = "^3.7" }
-mdformat = {version = "^0.6", python = "^3.8"}
-mdformat-gfm = {version = "^0.2", python = "^3.8"}
+mdformat = "^0.6"
+mdformat-gfm = "^0.2"
 mypy = "^0.930"
 pre-commit = "^2.7.1"
 pre-commit-hooks = "^3.3.0"
@@ -60,6 +60,7 @@ reorder-python-imports = "^2.3.5"
 safety = "^1.9.0"
 toml = "^0.10.1"
 tox = "^3.20.0"
+types-toml = "^0.10.1"
 
 [build-system]
 requires = ["poetry-core>=1.0.0"]