Add missing typing_exentions package to requirements.txt.

HexDecimal · HexDecimal · commit ef815aef9726 · 2021-01-02T16:10:31.000-08:00
Docs were failing to import tcod due to this missing module. Fixes #105
diff --git a/requirements.txt b/requirements.txt
@@ -2,3 +2,4 @@ cffi~=1.13
 numpy~=1.10,!=1.16.3;
 pycparser>=2.14
 setuptools>=36.0.1
+typing_extensions
