Applications: add setter to frequency

[matt1432]

I wanted to have a setter for frequency to be able to launch apps from the applauncher without using the launch() function, while still having the benefit of keeping track of frequency.

I wasn't satisfied with the resolution of #50, so this is my take on it.

Basically, instead of doing app.launch(), I do this:

Utils.exec(`hyprctl dispatch exec ${app.executable}`);
++app.frequency;

[kotontrion]

I know this got already merged, but I don't like that the launched signal is emitted when setting the frequency. Wouldn't this result in emitting the signal twice when using the launch method?

[Aylur]

the launch method increments the internal value and not through the setter