Drop support for old node versions

[Belco90]

Drop support for node v12, which reaches EOL in 2022-04-30, and node v17, which reaches EOL in 2022-06-01

Update Node.js engine requirement to ^18.18.0 || >=20.0.0, which is the same requirement that ESLint v9 will impose. This means we are dropping support for Node 12, 15, 16, 17, 19, and Node 18 versions prior to 18.18.0.

[MichaelDeBoey]

We should wait & see what ESLint will be doing to get to the same minimal version imo

[Belco90]

ESLint keeps supporting node v12, v14, v16 and greater. We can leave this for a future major then.