Document that Tea extension is a collection of best practices

[lukaszuznanski]

Goal

Document in the README and the docs that the Tea example is an opiniated example recommended best practices, and that is does not serve as a source for official requirements for TYPO3 extensions.

Acceptance criteria

• it is documented in the README and the docs that the Tea example is a collection of best practices

Additional Information

As the Tea example is not a best practice example in itself (with all the tools in it), but a collection of best practices. So we should document this to our Tea extension README and the extension manual. (Note: The minimal example will be auto-created from the CPS project builder template in the future.)