You need a documentation written in reStructuredText and as a Sphinx project. Please visit https://wiki.typo3.org/ReST for further information. You may consider using TYPO3 extension Sphinx to easily set up your environment and work on your own documentation.
The main documentation file should be named
Index.rst (to match the convention of the TYPO3 Documentation Team).
If you choose to name it “index.rst” instead (lower case), or want to use another arbitrary name, make sure to update
the default TypoScript settings accordingly.