Add an example in TextWrapping::overflow_character documentation

So people have a place to copy `…` from,
which is what most will probably want to use.

epaint/src/text/text_layout_types.rs

@@ -272,7 +272,7 @@ pub struct TextWrapping {
     /// Don't try to break text at an appropriate place.
     pub break_anywhere: bool,
 
-    /// Character to use to represent clipped text.
+    /// Character to use to represent clipped text, `…` for example.
     pub overflow_character: Option<char>,
 }