Native: Split dioxus-native-dom crate out of dioxus-native

[nicoburns]

Splits dioxus-native into two crates:

• dioxus-native-dom which contains:
  • The DioxusDocument
  • The MutationsWriter
  • Event types and conversions
• dioxus-native which contains everything else (application, launch, asset handling, etc).

The idea is that for use cases where you want to embed Dioxus Native into another application (e.g. a Bevy game) you can just use dioxus-native-dom and avoid pulling in Winit, Muda, etc.

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P.S. dioxus-native-dom could alternatively be called dioxus-native-core. I wasn't sure if it was better to reuse that name or leave being what it used to be.