Support deleting items from the custom commands history

In the custom commands panel you can now tab to the suggestions and hit 'd' to
delete items from there. Useful if you mistyped a command and don't want it to
appear in your history any more.

pkg/gui/controllers/suggestions_controller.go

@@ -43,6 +43,12 @@ func (self *SuggestionsController) GetKeybindings(opts types.KeybindingsOpts) []
 			Key:     opts.GetKey(opts.Config.Universal.TogglePanel),
 			Handler: func() error { return self.c.ReplaceContext(self.c.Contexts().Confirmation) },
 		},
+		{
+			Key: opts.GetKey(opts.Config.Universal.Remove),
+			Handler: func() error {
+				return self.context().State.OnDeleteSuggestion()
+			},
+		},
 	}
 
 	return bindings