Add support for node 20; drop node 16/17 support

[chris-griffin]

While all of our internal projects utilize node 18 currently, we will migrate to node 20 in 2024. As a result, we should ensure that this project supports node 20 which will become the new node LTS.

See https://endoflife.date/nodejs for timelines of each node release

Acceptance Criteria

• Drops support for node 16 via major release
• Drops support for node 17 via major release
• Adds support for node 20

[wrbrand]

Checking off the first two to-dos here as to-done:

design_system/package.json

Lines 11 to 13 in bb434d3

	"engines": {
	"node": ">=18"
	},