Add documentation to XkbToControl While some transformations are defined in the section “Interpreting the Control Modifier” of the XKB protocol, a lot are not. Documentation is scarce about the topic, so write down some context using the following sources: - https://en.wikipedia.org/wiki/Caret_notation#Use_in_software - https://www.vt100.net/shuford/terminal/dec_keyboards_news.txt - https://misc.openbsd.narkive.com/NvSWf6ax/which-key-shortcuts-are-safe-to-bind-and-some-q-s-about-history-and-os-diffs-re-ctrl-4-means - https://vt100.net/docs/vt220-rm/chapter3.html#T3-5