refactor: replace toasts_winrt with winrt-Namespace packages

[DatGuy1]

Better maintained by third party and resolves the concern that made me create the first party package to begin with. Closes #106

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (689c6bd) 97.75% compared to head (9974f9d) 97.75%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #113 +/- ## ======================================= Coverage 97.75% 97.75% ======================================= Files 10 10 Lines 624 624 Branches 89 89 ======================================= Hits 610 610 Misses 9 9 Partials 5 5 ```

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[DatGuy1]

I'm not /too/ miffed about dropping 3.8 support, but this is still something I'd rather avoid. I'll look into some PEP 508 way to use toasts_winrt after making sure the PR works fine on my local machine for a week or so, and then merge the PR and release 1.0.2/1.1.0 (TBD).

[Safihre]

Oh I didn't see that they required Python 3.9! You could also specify the fat winsdk package as requirement for 3.8 only? Since it also includes all the namespaces and probably doesn't required hacks in the main code to use toasts_winrt.

[DatGuy1]

There really isn't a very good way to do this and the stats show 3.8 isn't used a lot with the package, so I've dropped support for it entirely. People who still use 3.8 can use previous versions of the package. I may add a version matrix at a later date.

[DatGuy1]

Keeping unversioned for now

[Safihre]

Thanks 👍👍