* Add support for C# 12
* Run all tests on all major .NET SDKs
* Only build on Ubuntu
* Do not build docs for pull requests
* Add Cédric Luthi, and Frank Ray to authors
* Drop netstandard2.0 for ImageSharp plugin
When running on .NET Framework, the `Should_Report_Max_Remaining_Time_For_Extremely_Small_Progress` would intermittently fail with the following error:
```
task.RemainingTime
should be
10675199.02:48:05.4775807
but was
null
```
This is because it's possible that the two increment share the same timestamp thus making the `RemainingTime` null. To ensure the two increments don't share the same timestamp, we sleep for one millisecond.
Although I have only observed this issue on .NET Framework it would be possible that it occasionally also occur on .NET Core.
