mysql-native release v3.0.2

[Steven Schveighoffer]

This release is a complete overhaul of the CI system and dub files. 
Instead of using travis-ci (which now requires "credits", and I burned 
through all the free credits in one test run), it is using github 
actions. This also has the benefit of running much faster, though the 
integration tests no longer run on Windows or MacOS (this is a current 
limitation of github that I expect eventually will be solved). Very 
little has changed in terms of functionality, the exception being a 
now-default collation of utf8mb4 (as recommended 
[here](https://adamhooper.medium.com/in-mysql-never-use-utf8-use-utf8mb4-11761243e434)).

The recent issue with DMD 2.095 (specifically dub) not being able to 
build with mysql-native should be resolved.

Please see the 
[changelog](https://github.com/mysql-d/mysql-native/blob/master/CHANGELOG.md) 
for release notes. File any issues on the github project, especially any 
issues with your project no longer building with it.

Next I will likely be releasing the safe update (after I rebase it onto 
this new layout).

-Steve