Match locale names longest-first so a name that is a prefix of another parses

[spokodev]

Problem

formatRe builds a parser for a locale field (months, weekdays, periods) by
joining the names into an ordered regex alternation:

function formatRe(names) {
  return new RegExp("^(?:" + names.map(requote).join("|") + ")", "i");
}

JavaScript alternation is first-match, not longest-match: (?:a|b|…)
returns the first alternative that matches at the position. When an earlier
name is a prefix of a later name in the same field, the parser matches the
short name first, and the leftover characters then break the parse.

This silently corrupts d3's own formatter output in shipped locales:

const cs = timeFormatLocale(/* locale/cs-CZ.json */);
cs.format("%d %B %Y")(new Date(2020, 6, 15)); // "15 červenec 2020"
cs.parse ("%d %B %Y")("15 červenec 2020");    // null  ← should be 2020-07-15

"červen" (June) is a prefix of "červenec" (July). Same failure for Turkish
"Pazar" (Sun) vs "Pazartesi" (Mon), and "Cuma" (Fri) vs "Cumartesi"
(Sat): a utcParse("%Y %U %A") round-trip over 2020 in tr-TR fails on all
104 Mondays and Saturdays. vi-VN months ("Tháng 1" vs "Tháng 10/11/12")
are affected too.

Fix

Sort the names by descending length before building the alternation, so the
longest matching name wins. formatLookup is keyed by the matched text, so the
reordering does not affect index resolution:

names.slice().sort((a, b) => b.length - a.length).map(requote).join("|")

.slice() keeps the caller's array (shared with formatLookup) unmutated.

Test

Added a test/locale-test.js case that formats and re-parses a date in the two
shipped locales with the prefix collisions (Czech July, Turkish Monday). Fails
on main, passes with the fix. Verified no regression: en-US full/short month
and weekday round-trips over all months/days still pass, and eslint is clean.

[Fil]

lgtm, but can you please tighten the comments? They contain redundant explanations.

For example I would strip "; ordered alternation is first-match, not longest-match. formatLookup is keyed by text, so order is irrelevant to it." and " Ordered alternation matched the shorter name first, so these formatted dates failed to round-trip."

[spokodev]

Trimmed both — kept the sort rationale and the example names, dropped the rest.