E2E test harness for Svelte

"Yarn workspaces" uses its understanding of the build graph in a limited way, so to recompile and run just this set of E2E tests, you can run these commands at the project root:

yarn workspace @builder.io/e2e-app run build
yarn workspace @builder.io/e2e-svelte run build
yarn workspace @builder.io/e2e-svelte run e2e