🧹 Versioning: Bump minimum Node.js version from 18.18.0 to 20.19.0

[JoshuaKGoldberg]

Overview

We're gearing up for a new major version of Mocha, Mocha 12 (#5357). That means we can bump the minimum Node engine version! Hooray! This is great for a couple of reasons:

• It unblocks bumping old package versions, e.g. 📦 Package: Bump supports-color from 8 to 10 #5335
• It means we can use newer JavaScript + platform features

Node.js 18 went EOL April 30 2025. Node.js 20 is still LTS for another year, through April 30 2026. Node.js ^20.19.0 || >=22.12.0 is the minimum version that supports unflagged require(ESM).

So, our current thought for Mocha 12 is to raise the minimum Node.js version to ^20.19.0 || >=22.12.0.

Note: see #5226 -> #5354 for our policy on supported browser versions (still in review at time of posting). Node.js 20.0.0 was released on April 18, 2023, so the equivalent browser versions would be:

• Chrome 112
• Edge 112
• Firefox 112
• Safari 16.4