Editorial: Clean up structure, references, and common patterns

[gibson042]

This PR can be reviewed in entirety, or commit by commit.

First clean build in a long time! https://github.com/tc39/ecma402/pull/562/checks?check_run_id=2303361976

******> npm run "build-master"

> [email protected] build-master /home/runner/work/ecma402/ecma402
> mkdir out && cp -R img out && ecmarkup --lint-spec --verbose spec/index.html out/index.html --css out/ecmarkup.css --js out/ecmarkup.js

[2021-04-09T06:03:58.006Z] Loading biblios...
[2021-04-09T06:03:58.049Z] Loading imports...
[2021-04-09T06:03:58.492Z] Building boilerplate...
[2021-04-09T06:03:58.579Z] Linting...
[2021-04-09T06:03:58.806Z] Walking document, building various elements...
[2021-04-09T06:03:59.934Z] Building SDO map...
[2021-04-09T06:04:00.029Z] Finding offsets for replacement algorithm steps...
[2021-04-09T06:04:00.029Z] Autolinking terms and abstract ops...
[2021-04-09T06:04:01.974Z] Linking xrefs...
[2021-04-09T06:04:02.091Z] Linking non-terminal references...
[2021-04-09T06:04:02.092Z] Linking production references...
[2021-04-09T06:04:02.092Z] Building reference graph...
[2021-04-09T06:04:02.121Z] Highlighting syntax...
[2021-04-09T06:04:02.223Z] Building table of contents...
[2021-04-09T06:04:02.286Z] Found existing js link to ecmarkup.js, skipping inlining...
[2021-04-09T06:04:02.297Z] Found existing css link to ecmarkup.css, skipping inlining...
[2021-04-09T06:04:02.388Z] Done.
[2021-04-09T06:04:02.388Z] Writing output...
got status code 0

[ryzokuken]

LGTM, thanks!

[ryzokuken]

@gibson042 can we merge this?

@leobalter @sffc @FrankYFTang one additional review would be great :D

[ryzokuken]

Editorial PR with multiple approvals and editor sign-offs, merging.