bpo-33378: Add Korean to the language switcher. (GH-6627)

diff --git a/Doc/tools/static/switchers.js b/Doc/tools/static/switchers.js
index 8e0c5ea..3dea08e 100644
--- a/Doc/tools/static/switchers.js
+++ b/Doc/tools/static/switchers.js
@@ -21,6 +21,7 @@
       'en': 'English',
       'fr': 'French',
       'ja': 'Japanese',
+      'ko': 'Korean',
   };
 
   function build_version_select(current_version, current_release) {