docs: add section for RFCs

After proposals discussions on the mailing list, RFCs shape the
current or future status of Avocado.  It makes sense to archive
them for future reference.

Also some RFCs are constantly referred in other parts of the
documentation, so it makes sense to allow cross references between
them.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

docs/source/index.rst

@@ -68,6 +68,15 @@ Avocado Release Notes
 
    release_notes/index
 
+===========================
+Request For Comments (RFCs)
+===========================
+
+.. toctree::
+   :maxdepth: 1
+
+   rfcs/index
+
 Indices and tables
 ==================
 

docs/source/rfcs/index.rst

+===========================
+Request For Comments (RFCs)
+===========================
+
+The following list contains archivals of accepted, Request For
+Comments posted and discussed on the `Avocado Devel Mailing List`_.
+
+.. toctree::
+   :maxdepth: 1
+
+.. _Avocado Devel Mailing List: https://www.redhat.com/mailman/listinfo/avocado-devel