added py3.8, py3.9 and py3.10

[ddurham2]

alternative to #18 that only adds support for new python versions. Tests passed on 3.8 for me.

[kata198]

I have merged your changes and released 4.3.6 to github.
I am not yet sure how to publish to pypi from my phone, due to personal changes in my life I no longer have a computer. I will look into alternative methods to build and submit the package this weekend.
If you can build branch 4.3.6 and attach it, it may be helpful. Thanks!