Add codio support

[vinayak-mehta]

#20 implements this, opening this issue for some discussion.

Demo:

Color:

Progress bar:

[vinayak-mehta]

Right now, you can specify a codio in a yaml file as a list of prompt, input and output pairs, where the input is printed one letter at a time, and the output all at once. For example:

speed: 2
steps:
- prompt: $
  in: smol-git push origin master
  out: ''

Is this a good way to write a codio? I guess the best way would be to build a helper tool present-record which can record a terminal session when launched, and produce a codio file which present can use. But if you were to specify the codio by hand for now, would the above yaml (a file separate from your slides.md) be a good interface to do that? Or would something that you can specify inside your slides would be better? (like below)

prompt=$ input='smol-git push origin master' output=''

One problem with this format and the current implementation is that progress bars have to be specified as an input (so that they get printed one letter at a time), which is kinda wrong as progress bars are usually a part of the output.

speed: 2
- prompt: ''
  in: ████████████████████████
  out: ''

[vinayak-mehta]

I think that for now, an API (where a progress bar is a separate entity) similar to termynal would be a good way to go. In the future, a utility to convert terminalizer or asciinema outputs might be another way. Or maybe a utility which records and outputs in present format.