🏷️✨ finally migrate rm'd styleguide handbook conventions

[OpenINFbot]

last note worth mentioning on styleguide conventions
similar to those seen elsewhere: we used to
have our own freaking baby styleguide in our top-level
org dotrepo:

🔗 OpenINF/.github@f720bce

in retrospect, i do not change my opinion about that being the wrong place for that handbook sub-project, which i was imagining would outgrow (in amount of content) the repo it had started in and the dot-prefix-namesake would soon have made no sense at all

regretting my decision of not migrating it else where tho

Originally posted by @DerekNonGeneric in #1106 (comment)

[DerekNonGeneric]

here's an excellent example of something we'd like the initial pr to have handled:

🔗 https://gist.github.com/DerekNonGeneric/7a1b2a9375700f7a6b7f848f0ef36604