Remove Node.js 14 support

[ybiquitous]

Which issue, if any, is this issue related to?

Closes #6740
Closes #6785
(Unfortunately, the PR's author doesn't respond)

Is there anything in the PR that needs further explanation?

Node.js 16.13.0 is the first version of Node.js 16.x LTS series.
See https://nodejs.org/en/blog/release/v16.13.0

---

Here's a ls-engines report:

$ npx ls-engines@latest
`node_modules` found; loading tree from disk...
┌────────┬─────────────────────────────────────────────────────────────────┐
│ engine │ Currently available latest release of each valid major version: │
├────────┼─────────────────────────────────────────────────────────────────┤
│ node   │ v20.3.1, v19.9.0, v18.16.1, v17.9.1, v16.20.1                   │
└────────┴─────────────────────────────────────────────────────────────────┘

┌───────────────────────────────────┬───────────────────────────┐
│ package engines:                  │ dependency graph engines: │
├───────────────────────────────────┼───────────────────────────┤
│ "engines": {                      │ "engines": {              │
│   "node": "^16.13.0 || >= 18.0.0" │   "node": ">= 16.13"      │
│ }                                 │ }                         │
└───────────────────────────────────┴───────────────────────────┘


Your “engines” field allows fewer node versions than your dependency graph does.

If you want to widen your support, you can run `ls-engines --save`, or manually add the following to your `package.json`:
"engines": {
  "node": ">= 16.13"
}

┌────────┬─────────────────┬─────────────────┬──────────────────────────┐
│ engine │ current version │ valid (package) │ valid (dependency graph) │
├────────┼─────────────────┼─────────────────┼──────────────────────────┤
│ node   │ v20.3.0         │ yes!            │ yes!                     │
└────────┴─────────────────┴─────────────────┴──────────────────────────┘

[changeset-bot]

🦋 Changeset detected

Latest commit: f194ae7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
stylelint	Major

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[mattxwang]

LGTM!

[Mouvedia]

In the same way as

stylelint/docs/migration-guide/to-15.md

Line 186 in 21dfacb

- removed support for Node.js 12

we need a breaking change(s) section for to-16.

[ybiquitous]

@Mouvedia Good catch! Updated via f194ae7.

[jeddy3]

LGTM, thank you.