Raise minimum Node.js version to v20

[asamuzaK]

• .github/workflows/build.yml
  Drop node v18 and add node v22 as lts/*
• package.json
  Bump engines.node to >=20
• lib/properties/font.js
  Switch to Array.prototype.toReversed()
• scripts/generateImplementedProperties.mjs
  • Switch to import.meta.dirname
  • Sort generated properties

Done below

TODO:
Fix properties/font.js after #227 get merged.

TBD:
Should we fix scripts/generateImplementedProperties.mjs too?
However, import.meta.dirname is not standard.

[domenic]

TBD:
Should we fix scripts/generateImplementedProperties.mjs too?
However, import.meta.dirname is not standard.

I think we should fix it. import.meta is not governed by standards, so since we are running on Node.js, we can use anything that they officially support. Per https://nodejs.org/api/esm.html#importmetadirname import.meta.dirname is officially supported.