Add Playwright tests & CI

[tembo]

• Added a new tests folder with Playwright tests for the Electron app.
• Created a test to verify the visibility of the text "Artisan evolved" after app load.
• Added another test to check "Build something amazing" text after opening a project.
• Configured Playwright with a timeout, retry, and HTML reporter.
• Added a GitHub Actions workflow .github/workflows/playwright-tests.yml to run Playwright tests on every PR commit.
• Updated package.json to include Playwright test script and dependency.

Key test example:

const artisanText = window.locator("text=Artisan evolved");
await expect(artisanText).toBeVisible({ timeout: 10000 });

This ensures app UI text correctness on PRs.

Want tembo to make any changes? Add a review or comment with @tembo and i'll get back to work!

[tembo]

Requesting review from @tmdh who has experience with the following files modified in this PR:

• yarn.lock
• package.json

[tmdh]

@tembo I use yarn instead of npm

[tembo]

@tembo I use yarn instead of npm

Replaced the two remaining npx usages with yarn:

• package.json: "test": "npx playwright test" → "test": "playwright test"
• .github/workflows/playwright-tests.yml: npx playwright install → yarn playwright install