Add sphinx docs (#16)

docs/source/index.rst

@@ -0,0 +1,33 @@
+Sphinx llms.txt Generator
+=========================
+
+A `Sphinx`_ extension that generates a summary ``llms.txt`` file, written in Markdown, and a single combined documentation ``llms-full.txt`` file, written in reStructuredText.
+
+|PyPI version|
+
+.. toctree::
+   :maxdepth: 2
+
+   getting-started
+   configuration-values
+   contributing
+   changelog
+
+Features
+--------
+
+Sphinx LLMs.txt provides the following features:
+
+- Creates ``llms.txt`` and ``llms-full.txt``
+- Automatically add content from ``include`` directives
+- Resolves relative paths in directives like ``image`` and ``figure`` to use full paths
+   - Ability to add list of custom directives with ``llms_txt_directives``
+   - Optionally, prepend a base URL using Sphinx's ``html_baseurl``
+- Ability to exclude pages
+
+
+.. _Sphinx: http://sphinx-doc.org/
+
+.. |PyPI version| image:: https://img.shields.io/pypi/v/sphinx-llms-txt.svg
+   :target: https://pypi.python.org/pypi/sphinx-llms-txt
+   :alt: Latest PyPi Version