e2e: Initialize end to end testing

[juliaogris]

Initialize end to end testing in top level directory e2e.

On CI e2 testing runs against https://evy.dev at the moment!

Initialize e2e node package with

echo '{"private": true}' > e2e/package.json
npm install --save-dev --prefix e2e playwright
npm install --save-dev --prefix e2e @playwright/test@latest

Add node_modules/ to .gitignore.

Add a minimal index.test.js test file that loads the Evy playground index.html
page. It runs two tests on it:

• ensure the title is "Evy | Playground"
• execute Run and ensure the console output contains expected contents.

Setup basic playwright test config that will allow to parametrize the baseURL
for tests - it expects a BASEURL environment variable and falls back to https://localhost:8080 by default. For local development run

SERVEDIR_PORT=8080 make serve

and in other terminal

cd e2e; npx playwright test [--ui]

Add e2e target to make file, triggered by ci target.
If BASEURL environment variable is not set, make will set it to https://evy.dev
for now. This allows us to prototype e2e testing until we can extract the per-PR
preview deployment URL from the firebase-deploy run.
We will add this in a follow up PR.

Despite concerns it seems that the CI runtime has increased by only less than 30 seconds at this stage.

Part 1/2 for evylang/todo#43

[github-actions]

firebase-deployment for dbbc43d

• apex: https://evy-lang-stage--238-tadpcime.web.app
• discord: https://evy-lang-stage-discord--238-n7v77zjq.web.app
• docs: https://evy-lang-stage-docs--238-rhhpgbmm.web.app
• learn: https://evy-lang-stage-learn--238-xh04f7hx.web.app
• play: https://evy-lang-stage-play--238-3n7f9stk.web.app