Add link to Pyodide's ffi docs

Author: hoodmane

peps/pep-0776.rst

@@ -731,7 +731,9 @@ Because Emscripten supports POSIX, a significant number of tasks can be achieved
 using the ``os`` module. However, many fundamental operations in JavaScript
 runtimes are not possible via POSIX APIs. Pyodide's approach is to specify a
 mapping between the JavaScript object model and the Python object model and a
-calling convention that allows high level bidirectional integration.
+calling convention that allows high level bidirectional integration. `See the
+Pyodide documentation here
+<https://pyodide.org/en/stable/usage/type-conversions.html>`__.
 
 Asyncio
 ~~~~~~~