feat(www): playwright test setup

[trm217]

• feat(container): buildpack container poc
• feat(container): add yarn build:cnb script
• fix(container): move buildCNBContainer out of main
• feat(container): allow build env to be passed by args
• fix(container): pack download dir creation
• test: start creating testcontainers setup
• test(www): move playwright setup into www and run against dev server
• test(www): allow running e2e test against www dev or prod build
• test(www): configure playwright to allow creating screenshots
• test(www): add screenshots from 'checkout' visual tests