Refresh README examples

[bradlarsen]

The example snippets and usage instructions in the README are out-of-date now. They could also stand to be generally improved.

Some ideal properties of the example usage snippets:

• they can be automatically regenerated from a script
• they include short animation screen captures, in addition to static terminal command/output text

Useful references:

• Make Your CLI Demos a Breeze with Zero Stress and Zero Mistakes
• https://github.com/paxtonhare/demo-magic
• https://github.com/faressoft/terminalizer

[bradlarsen]

Note, terminalizer is half implemented and crashes when generated gifs for me. I have had much better luck using asciinema for recording and agg for rendering.

[bradlarsen]

Another tool for terminal session recording, screenshot capture, and gif creation: https://github.com/charmbracelet/vhs

[bradlarsen]

I ended up using vhs for creating some example GIFs in #154. That works usably well. The project is cool, but has a lot of significant bugs in it.

The most robust combination of tools I've tried for scripting and recording terminal sessions is demo-magic for scripting, asciinema for recording, and agg for rendering.