Enable type checking on PR builds

[ahsan-z-khan]

Describe the feature you'd like
Enable type checking PR builds. mypy type checker is not enabled on the PR builds.
https://github.com/aws/sagemaker-python-sdk/blob/master/tox.ini#L133

How would this feature be used? Please describe.
It will enable static type checking on the code during PR builds.

Additional context
This needs to be enables during PR builds

[testenv:typing]
deps = mypy
commands =
    mypy src/sagemaker

[liujiaorr]

Any update if feature request has been processed or still in needed?

[liujiaorr]

Check has been added, close the issue