[FEATURE] Scaffold Playwright for E2E testing

[disposedtrolley]

Is your feature request related to a problem? Please describe.

As an outcome of #10, scaffold some basic Playwright tests to ensure core functionality works as expected.

Describe the solution you'd like

Playwright tests that exercise core functionality of the site. Tests should run against Vercel preview builds in PR branches and against prod after merging to main.

The scope of the initial work should cover:

• Setting up a Playwright configuration and single test case.
• Adding a GH Actions job to execute Playwright against the appropriate Vercel build (need to figure out if it’s possible to fetch the URL that Vercel generates for preview builds, or alternatively if the URL is deterministic against the branch name, how we can dynamically compute the URL)

[disposedtrolley]

Unassigning myself as I don't think I have capacity to work on this ATM.

[MatthewCaseres]

I don't think anybody else is going to tackle this issue. I don't think we need it. Please close.