docs: replace Sphinx/ReadTheDocs with DeepWiki

Remove outdated Sphinx documentation and add DeepWiki badge for
auto-generated documentation that stays current with the codebase.

Author: titusz

.gitignore

@@ -48,9 +48,6 @@ htmlcov
 output/*.html
 output/*/index.html
 
-# Sphinx
-docs/_build
-
 .DS_Store
 *~
 .*.sw[po]

README.md

@@ -2,6 +2,7 @@
 
 [![PyPI Package](http://img.shields.io/pypi/v/onixcheck.svg?style=flat-square)](https://pypi.python.org/pypi/onixcheck)
 [![PyPI Downloads](http://img.shields.io/pypi/dm/onixcheck.svg?style=flat-square)](https://pypi.python.org/pypi/onixcheck)
+[![DeepWiki](https://deepwiki.com/badge.svg)](https://deepwiki.com/titusz/onixcheck)
 
 ## Introduction