Add mypy configuration, typing fixes

Author: wkeeling

pyproject.toml

@@ -18,3 +18,8 @@ line_length = 119
 multi_line_output = 3
 use_parentheses = true
 include_trailing_comma = true
+
+
+[tool.mypy]
+exclude = "thirdparty"
+

seleniumwire/request.py

@@ -19,6 +19,8 @@ def __repr__(self):
 class Request:
     """Represents an HTTP request."""
 
+    _body: bytes
+
     def __init__(self, *, method: str, url: str, headers: Iterable[Tuple[str, str]], body: bytes = b''):
         """Initialise a new Request object.
 
@@ -119,7 +121,7 @@ def host(self) -> str:
         """
         return urlsplit(self.url).netloc
 
-    @path.setter
+    @path.setter  # type: ignore
     def path(self, p: str):
         parts = list(urlsplit(self.url))
         parts[2] = p