Add suggestions support

The new option `app.Suggest` enables command and flag suggestions via
the jaro-winkler distance algorithm. Flags are scoped to their
appropriate commands whereas command suggestions are scoped to the
current command level.

Signed-off-by: Sascha Grunert <sgrunert@suse.com>

docs/v2/manual.md

@@ -34,6 +34,7 @@ cli v2 manual
   * [Version Flag](#version-flag)
     + [Customization](#customization-2)
   * [Timestamp Flag](#timestamp-flag)
+  * [Suggestions](#suggestions)
   * [Full API Example](#full-api-example)
 
 <!-- tocstop -->
@@ -1426,6 +1427,13 @@ In this example the flag could be used like this :
 
 Side note: quotes may be necessary around the date depending on your layout (if you have spaces for instance)
 
+### Suggestions
+
+To enable flag and command suggestions, set `app.Suggest = true`. If the suggest
+feature is enabled, then the help output of the corresponding command will
+provide an appropriate suggestion for the provided flag or subcommand if
+available.
+
 ### Full API Example
 
 **Notice**: This is a contrived (functioning) example meant strictly for API