Add FAQ and "why"s to README

[elukoyanov]

Currently, project is works and show a simple example of project structure and tests.

But, some JS/TS/Codecept newbies don't know what to pay attention.

• [ ] Why and where the tsconfig is placed. How is it used. Why are 2 tsconfig placed in repository.
• [ ] Where types for Codecept are placed and how them can be updated.
• [ ] How to work with Windows OS. What are the differences.