Group management section, add redirect

Signed-off-by: Adam Warner <me@adamwarner.co.uk>

docs/group_management/index.md

@@ -1,5 +1,3 @@
-## Group management
-
 Any blocklist or domain on the white-/black-/regex-lists can be managed through groups. This allows not only grouping them to highlight their relationship, but also enabling/disabling them together if one, for instance, wants to visit a specific service only temporarily.
 
 Group `Default` (`group_id` `0`) is special as it is automatically assigned to domains and clients not being a member of other groups. Each newly added client or domain gets assigned to group zero when being added.

mkdocs.yml

@@ -148,8 +148,8 @@ nav:
         - 'Debugging':
             - 'gdb': ftldns/debugging.md
             - 'valgrind': ftldns/valgrind.md
-  - 'Group management':
-    - 'Overview': group_management/groups.md
+  - 'Group Management':
+    - 'Group Management': group_management/index.md
     - 'Examples': group_management/example.md
   - 'RegEx blocking':
     - "Overview": regex/overview.md
@@ -271,3 +271,4 @@ plugins:
         'database/gravity/index.md': database/domain-database/index.md
         'database/gravity/recovery.md': database/domain-database/recovery.md
         'database/gravity/groups.md': database/domain-database/groups.md
+        'group_management/groups.md': group_management/index.md