efl_ui_button: improve docs

Reviewers: segfaultxavi

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D9963

src/lib/elementary/efl_ui_button.eo

@@ -6,6 +6,10 @@ class Efl.Ui.Button extends Efl.Ui.Layout_Base implements Efl.Input.Clickable, E
 
      Press it and run some function. It can contain a simple label and icon
      object and it also has an autorepeat feature.
+
+     The icon can be set using @Efl.Content.content, the text can be set using @Efl.Text.text.
+
+     The events of @Efl.Input.Clickable can be used to listen to a click event from the user.
    ]]
    implements {
       class.constructor;