test create-svelte deployments

[Rich-Harris]

On the Kit repo we used to deploy the template on each PR, e.g. to https://cloudflare.demo.svelte.dev. It's a good way to ensure that things are working end to end. Now that create-svelte no longer lives in the kit repo, those deployments have started failing.

Not sure if they should live here, or still in Kit because they're really testing the adapters as much as the template, but I wanted to leave a note somewhere before I kill off the project on Cloudflare Pages

[benmccann]

The deployments were a pain in the butt. But testing creating a project and then hitting it with playwright would be helpful

[manuel3108]

This was done as part of #275. We are not only testing the templates, but additionally most of the addons