Create Style Guidelines

[almann]

We should have style guidelines around things like column width for our source files and make sure all of the source files are consistent with it.

Originally posted by @almann in https://github.com/partiql/partiql-spec/pull/30#discussion_r965239780

[jpschorr]

Here are the official recommendations.

Of note, they recommend a single sentence per line. This is a recommendation I've used in writing LaTeX before with some dubious benefit. See an example here: https://raw.githubusercontent.com/progit/progit2/main/book/02-git-basics/sections/remotes.asc