runApp method
Boots the given app widget, handles signals, and starts rendering.
Implementation
void runApp(Widget app) {
terminal.clear();
terminal.hideCursor();
_rootElement = app.createElement();
_rootElement!.mount(null);
scheduleFrame();
ProcessSignal.sigint.watch().listen((_) => shutdown());
ProcessSignal.sigterm.watch().listen((_) => shutdown());
ProcessSignal.sigwinch.watch().listen((_) {
outputBuffer.resize();
});
}