Add basic local testing setup to generated extension

[alexander-nitsche]

Is your feature request related to a problem? Please describe.
The tests of a generated extension cannot be executed directly, but the user has to set up an individual test environment, e.g. using the official TYPO3 documentation, which is error-prone.

Describe the solution you'd like
The TYPO3 Core already has a runTests.sh that handles all test scenarios in a convenient and comprehensive docker way, supporting Linux / MacOs / Windows. Generating a similar runTests.sh together with the TYPO3 extension in the Extension Builder would give the user a tool to run unit/function/acceptance tests of the extension immediately and provide inspiration for an individual test environment.

[simonschaufi]

That is already on my todo list and also related to #430. The main question is if we want to use "the tea way of testing" or more like the core because tea doesn't use a runTests.sh.