Setup Cypress for E2E testing

[jeffpaul]

Is your enhancement related to a problem? Please describe.
See overall concept in the OSBP guide and example setups on Simple Podcasting, Restricted Site Access, and ElasticPress.

Describe the solution you'd like

• add base GitHub Action
• add .wp-env.json
• add base docker files
• update package.json / package lock files
• add cypress tests

Designs
n/a

Describe alternatives you've considered
n/a

Additional context
n/a