Overhaul docs.

- Document backporting
- Reference the cPython dev docs for everything else.
- Test docs and package summary.
diff --git a/NEWS b/NEWS
index ab72135..2aa442a 100644
--- a/NEWS
+++ b/NEWS
@@ -7,7 +7,7 @@
 - Issue #23581: Add matmul support to MagicMock. Patch by Håkan Lövdahl.
 
 - Issue #23326: Removed __ne__ implementations.  Since fixing default __ne__
-  implementation in issue #21408 they are redundant. **** NOT BACKPORTED ****
+  implementation in issue #21408 they are redundant. *** NOT BACKPORTED ***
 
 - Issue #21270: We now override tuple methods in mock.call objects so that
   they can be used as normal call attributes.