Allow public access to UseStreamDeck and IStreamDeckActionRegistry

[nguyenquyhy]

I would like to propose 2 changes:

• Allow public access to UseStreamDeck. This would be very beneficial to some complex setup such as integrating to WPF and reuse the ServiceProvider. Having direct access to UseStreamDeck means we can have more control on IHost instance to allow integration with more scenario.
• Register IStreamDeckActionRegistry to the service provider instead of StreamDeckActionRegistry. This allows library consumers to call RegisterAll on specific assemblies. This would be required to register StreamDeckAction in referenced library projects.

[GeekyEggo]

Hey @nguyenquyhy, I completely agree on all points, nice changes. 👍

There are recent breaking changes (relating to property inspectors) that require a v7 release. I will include your changes as part of this major release, which will also include basic support for Stream Deck+ SDK.

[nguyenquyhy]

Great. Can't wait for StreamDeck+ support! I can try to help out too. Thanks for all your effort. This library has been invaluable for my plugin.