chore(prettier): automatically wrap markdown files

[LeoMcA]

I really don't like manually wrapping markdown files.

Two parts: first commit makes the config change, second commit updates existing markdown files.

[fiji-flo]

I like it how about the rest of the team?
@Guyzeroth @caugner @schalkneethling

[fiji-flo]

@LeoMcA can you fix the failing test?

[queengooborg]

In mdn/content#6936, there was strong writer preference towards not wrapping lines in the Markdown (and I'm also in favor of not wrapping lines; I unwrap them whenever I get the chance). This PR updates Yari's internal files (though unintentionally affects content), but shouldn't we follow the same principles between content and yari?

[LeoMcA]

Oh dear, let me revert the .prettierrc changes to fix #6075, before figuring out how to apply those changes without affecting h2m.

shouldn't we follow the same principles between content and yari?

I wouldn't say so: the repos have different editors, and audiences.