Add base64 package

Author: fraya

docs/source/index.rst

@@ -24,5 +24,6 @@ Packages
 --------
 
 * `anaphora <https://dylan-lang.github.io/anaphora/>`_
+* `base64 <https://dylan-lang.github.io/base64/>`_
 * `binary-data <https://dylan-lang.github.io/binary-data/>`_
 * `testworks <https://dylan-lang.github.io/testworks/>`_