There's been a lot of work done on adding mount state functionality (thanks to @Dridus) to reflex-dom-core. This milestone collects up the work needed to get the mount state feature released.

Note:
0.5 added hydration, and we have to be careful about defining the interaction between these two features. A "mounted" widget should be one that is both in the DOM and hydrated. Some of the existing PRs will need to be updated to work with, and tested against the new hydration DOM builder.