Y26-081 - Sequencescape - Add Javascript Testing workflow

[andrewsparkes]

Describe the Housekeeping
Add a javascript testing workflow to Sequencescape so it runs on CI.

Blocking issues
NA

Additional context
See story #5565 which added some JS tests.

Similar JS testing in Limber uses this workflow:
https://github.com/sanger/limber/blob/develop/.github/workflows/test_js.yml