Update News entry.
diff --git a/Misc/NEWS b/Misc/NEWS
index 7b6dbd2..6a0c0e2 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -86,6 +86,8 @@
 Library
 -------
 
+- Issue #12798: Updated the mimetypes documentation.
+
 - Issue #13639: Accept unicode filenames in tarfile.open(mode="w|gz").
 
 - Issue #1785: Fix inspect and pydoc with misbehaving descriptors.