* implement events instead of interfaces
  Interfaces and the wrappers head the problem that they could not support multiple events at once or only a single one without loosing the others.
* add text input support for WASM on mobile
  A hidden html input is required to open the keyboard and receive the
  input.
* improve the number choice
  * fix using the default number
  * add submit button only if a onclick method was provided

This allows to not use the internal game state directly from client
code.

* Generalize hover detection and move it into ui.Collection
* Implement transparencu for the prompt banner