Implement the initial step definitions in tests/staging/step_definitions/website_steps.js

[dannystaple]

The file tests/staging/step_definitions/website_steps.js has some pending, empty steps.
Let's fill them in with playwright.

• Set up playwright as part of the test container.
• Setup an environment variable to tell the tests where to find the staging site. BASE_URL?
• The staging service in docker compose should have a well defined name in docker compose networking and port already, assign this as the default value for BASE_VALUE.
• The step Given the Staging site is started should verify that the BASE_URL can be reached.
• The step The index page is visited should ensure that it's loaded a page, with no HTTP error statuses
• The step Then the Logo should be displayed in the top left corner can merely check that favicon.png is somewhere nested under a <nav> element. It doesn't matter how many layers down for now.

Acceptance criteria

• Modified files conform to the .editorconfig file
• Playwright is used as part of the test run
• GitHub workflows run and pass
• The step definitions test the given criteria.
• The environment variable BASE_URL exists, and is used in the page goto section.
• The docker compose defaults mean no changes should be needed to the workflows

Additional information

Examples of combining gherkin with playwright at https://www.browserstack.com/guide/playwright-cucumber.