Adds Node version 20 compatibility

[PaulREnglish]

Issue Number

Issue: #108

Description

Addresses #108. Adds Node 20 compatibility to build tools including:

• setting the default Node version to 20
• fixes issues with npm dependencies and jest tests using Node 20.

Change Log

• Sets default Node version to 20 in nvmrc
• updates eslint-plugin-jsdoc package to 48.8.3
• Removes mock-fs to fixes issue where jest tests were failing in Node 20 (see Fix compatibility with Node 20 tschaub/mock-fs#384)
  • Instead we use memfs and unionfs to mock the file system.

Notes

• Contain changes from Add postcss-scss package to parse SCSS using Stylelint version 14 or higher #121. (I needed these changes for testing purposes.)
• In the project paths test, I've removed the code that loads the real node_modules file as the test all passes without it.
• The package.json still specifies that node version should be 16 or above as I don't think we want to remove support for the older Node versions yet. The Node version should now default to 20.

The merge-base changed after approval.

[ampersarnie]

Nice. Thank you.

The merge-base changed after approval.