Ken Dale

`UseInMemoryFeatureProvider` shouldn't be used except during local development since the settings don't survive when the application is shutdown. That said, `UseCachedSqlFeatureProvider` is the only viable option currently for _actual_ use....

The `internal` could be removed from this `set;`: https://github.com/ritterim/RimDev.FeatureFlags/blob/6a5bd6b6d0078ae570e1b1dd91cbe578a1e719e4/src/RimDev.AspNetCore.FeatureFlags/FeatureFlagOptions.cs#L19 I was thinking that the extension methods would be used instead, but `internal` does seem to prohibit using a custom provider....

Added a `UseCustomProvider` extension method in #27. If we want to change the overall philosophy and results in a breaking change we can look into that with v2.

This is tricky since the letters that display when there is no picture for a circle shine through the image. Also, the lines that are normally covered by a circle...

CI/CD added in #10.