feat: allow to see the command prompt followed by the executed command in the output image

[4zv4l]

It would be great if it was possible to get the command executed in the final image (using --execute), that way it will look like a "real" screenshot of a terminal.
If for limitation it isnt possible to capture the prompt, even a prompt as simple as:

$ <cmd>
<output>

would be amazing already.

[maaslalani]

Hey totally agree! We're working on this one in #44