LitWidget conditional events helpers

Helper functions for LitWidget conditional events.

• keydown() - keydown event helper;
• keyup() - keyup event helper;
• keypress() - keypress event helper.

You can specify one or more keyboard shortcuts:

class SampleWidget extends LitWidget {

  @onEvent('search-field', keydown('esc'))
  cancel(event) {
    ...
  }

  // or

  @onEvent('search-field', keydown(['esc', 'ctrl+k']))
  cancel(event) {
    ...
  }

}

For the keyboard shortcut format, see KeyboardShortcuts.