feat: Add TypeScript example.

[sainthkh]

For cypress-io/cypress#7806

[CLAassistant]

All committers have signed the CLA.

[sainthkh]

Waiting for fix in #512.

[sainthkh]

TypeScript test should fail until cypress/cypress#7806 is merged.

[bahmutov]

move it to fixtures test.html file :)

[sainthkh]

It cannot be removed entirely because it shows that the type of Test Runner window fails because it's not extended.

I rewrote the test like below:

  it('test extending AUTWindow', () => {
    // Test Runner window object doesn't have add() function.
    // So, it should fail the type check.
    // @ts-expect-error
    window.add = (a, b) => a + b

    cy.window().then((win) => {
      // AUT add() is defined in the fixture, test.html.
      // So, it should pass the type check.
      return win.add(2, 3)
    })

[bahmutov]

almost good - just need to move the window.add into the application's HTML file <script>...</script> tag, no need to confuse the matter by adding it to the before in the spec file

[bahmutov]

oh, one more thing - the example folder itself needs a README file with at least the basic description

[sainthkh]

Detailed explanation is in the official doc site. So, I made it simple here.

[bahmutov]

I think this looks good