Write tests in TypeScript without setting up preprocessors

From Cypress 4.4.0, you can write tests in TypeScript without setting up preprocessors. See the official doc for more details.

• Use out-of-the-box TypeScript.
• Write spec files, support files and configuration in TypeScript.
• Define type for the custom commands.
• Check types in the spec files.
• Show difference between Test Runner window and AUTWindow types. And how to extend AUTWindow type.