Update documentation to include Django 3.2 as supported version (#8037)

Author: FinnGu

README.md

@@ -53,7 +53,7 @@ There is a live example API for testing purposes, [available here][sandbox].
 # Requirements
 
 * Python (3.5, 3.6, 3.7, 3.8, 3.9)
-* Django (2.2, 3.0, 3.1)
+* Django (2.2, 3.0, 3.1, 3.2)
 
 We **highly recommend** and only officially support the latest patch release of
 each Python and Django series.

docs/index.md

@@ -84,7 +84,7 @@ continued development by **[signing up for a paid plan][funding]**.
 REST framework requires the following:
 
 * Python (3.5, 3.6, 3.7, 3.8, 3.9)
-* Django (2.2, 3.0, 3.1)
+* Django (2.2, 3.0, 3.1, 3.2)
 
 We **highly recommend** and only officially support the latest patch release of
 each Python and Django series.