enhancement/issue 1202 bump to minimum supported NodeJS LTS versions

[thescientist13]

Related Issue

resolves #1202

Documentation

1. Do we need to document minimum version in the website? - tracking here for now - docs/document new minimum NodeJS requirements for SSR custom loaders www.greenwoodjs.dev#159

Summary of Changes

1. Bumped minimum NodeJS version to 18.20.5 (for unflagged JSON modules)
2. Updated GitHub Actions to include runners for NodeJS 20.x / 22.x
3. Updated project to use Node 20.x

See here for an analysis of current features - #1202 (comment)

As part of #1220 , we'll likely shift the GitHub Actions from [18, 20] -> [20, 22], but we can probably keep the minimum version of 18.20.5 in the engines field either way

TODO

1. Should we actually set the engines to something like this, and maybe track stabilizing on one final >= version - stabilize to a single minumum NodeJS LTS version for engines #1379

   "engines": {
     "node": "^18.20.5 || ^20.10.0 || ^22.12.0"
   }

2. Can probably close these out
   • enhancement/upgrade project for Node 20 support #1203
   • enhancement/upgrade project for Node 22 LTS support #1307