Test session captures

[ghost]

FYI, I have generated several test session captures for terminal authors wishing to stress-test their sixel/image support at https://jexer.sourceforge.io/sixel.html

These tests create dozens-to-hundreds of small sixel (or iTerm2) images, and have taxed/crashed several terminals with sixel support. I plan to periodically add more captures at different text cell sizes, and more with iTerm2 images, but checking if a terminal can just handle it without crashing / excessive memory use / flickering doesn't require a matching cell size.