Improvements to handling of incoming events

[sholderbach]

To avoid issues with incoming resize events (#166) and improve performance in certain situations (pasting text via terminal facilities) restructure the event input processing:

• Drain all crossterm events currently available
• Prioritize the last resize and discard intermmediates
• Join all EditCommands to be processessed together before handing them to the internal event handler which will trigger a repaint

[sholderbach]

Note: previously lived unrelated under #164

[sophiajt]

This looks good to me. And trying it out, it's definitely a big improvement over what we had