Add ascii animation support

[chrisduerr]

This is a bit much, but I'm not aware of any other application that allows easily creating ascii animations. So it would be nice if sketch could help with that.

Fundamentally, this should be pretty simple. The following functionality should be useful for recording:

• When starting the recording, every action is recorded
• Pausing allows multiple actions in a single "frame"
• "Empty" frames can be inserted to extend the period one frame is visible

Instead of storing a single image, the recording should be a number of escape sequences necessary to get from one frame to the next one. Since newlines shouldn't be necessary as part of the payload, an encording might for example be that every single line is one "frame".

This methodology would be super flexible and allow for playback just using standard unix tools. An animation running at 1 FPS could be played like this for example:

for frame in $(cat recording); do printf "$frame"; sleep 1; done