docs: add index docs

docs/index.rst

@@ -6,8 +6,24 @@
 Welcome to MetaCall Jupyter Kernel's documentation!
 ===================================================
 
+MetaCall Jupyter Kernel is an open-source wrapper kernel that implements
+cross-language function calls through the `MetaCall Core`_ and the
+`Polyglot REPL`_. MetaCall Core is an open-source library that brings
+the polyglot programming experience to Developers. With MetaCall,
+developers can embed different programming languages through an
+easy-to-use high-level API.
+
+The Kernel exposes the MetaCall Core API which can be loaded and
+launched through a Jupyter Notebook interface. With this Notebook, the
+users can try out writing, mixing and embedding code in different
+programming languages.
+
+.. _MetaCall Core: https://github.com/metacall/core
+.. _Polyglot REPL: https://github.com/metacall/polyglot-repl
+
 .. toctree::
-   :hidden:
+   :maxdepth: 2
+   :caption: Contents:
 
    installation
    contributing