working hot reload for widget definitions

[Frizi]

Pull Request Description

Fixed a long-standing annoyance that widgets weren't fully hot-reloadable. Now when the widget definition (e.g. score function) is modified, it is hot-reloaded and new version immediately takes effect.

widget-hmr.mp4

Important Notes

Because of how HMR API works, it needs to be passed from each widget module to the widgetDefinition function as an argument. When not provided, the definition will not be hot-reloadable (but the widget will still work as it used to).

Checklist

Please ensure that the following checklist has been satisfied before submitting the PR:

• The documentation has been updated, if necessary.
• Screenshots/screencasts have been attached, if there are any visual changes. For interactive or animated visual changes, a screencast is preferred.
• All code follows the
  Scala,
  Java,
  and
  Rust
  style guides. In case you are using a language not listed above, follow the Rust style guide.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed, the GUI was tested when built using ./run ide build.