Setup E2E tests after converting this repo to Flowershow's template repo

[olayway]

Acceptance

• our old E2E Playwright tests are executed on each push to main and each PR against main
• they live in a separate repo: https://github.com/datopian/flowershow-template-e2e
• they can be run locally as well
• they have README with instructions on how to use them locally and in the CI
• all the tests pass

### Tasks
- [x] adjust [the e2e repo](https://github.com/datopian/flowershow-template-e2e) and its setup script to allow for local testing
- [x] add README to [the e2e repo](https://github.com/datopian/flowershow-template-e2e) with instructions
- [x] create E2E workflow in this repo

[olayway]

All done