Added: None Overload

[utsav00]

Solved: #4713

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

+ src/werkzeug/http.py:904: error: No overload variant of "parsedate_tz" matches argument type "str"
+ src/werkzeug/http.py:904: note:     def parsedate_tz(date: None) -> None
+ src/werkzeug/http.py:904: note: Possible overload variant:

+ starlette/staticfiles.py:213: error: No overload variant of "parsedate" matches argument type "str"
+ starlette/staticfiles.py:213: note:     def parsedate(date: None) -> None
+ starlette/staticfiles.py:213: note: Possible overload variant:
+ starlette/staticfiles.py:214: error: No overload variant of "parsedate" matches argument type "str"
+ starlette/staticfiles.py:214: note:     def parsedate(date: None) -> None
+ starlette/staticfiles.py:214: note: Possible overload variant:

+ aiohttp/web_response.py:318: error: No overload variant of "parsedate" matches argument type "str"
+ aiohttp/web_response.py:318: note:     def parsedate(date: None) -> None
+ aiohttp/web_response.py:318: note: Possible overload variant:
+ aiohttp/web_response.py:320: error: "datetime" gets multiple values for keyword argument "tzinfo"
+ aiohttp/web_request.py:474: error: No overload variant of "parsedate" matches argument type "str"
+ aiohttp/web_request.py:474: note:     def parsedate(date: None) -> None
+ aiohttp/web_request.py:474: note: Possible overload variant:
+ aiohttp/web_request.py:476: error: "datetime" gets multiple values for keyword argument "tzinfo"

[hauntsaninja]

Thanks, looks good!