do not spend time drawing text with is_visible = false (#893)

do not draw text with is_visible = false

crates/bevy_ui/src/widget/text.rs

@@ -153,6 +153,10 @@ pub fn draw_text_system(
     let vertex_buffer_descriptor = font_quad.get_vertex_buffer_descriptor();
 
     for (entity, mut draw, text, node, global_transform) in query.iter_mut() {
+        if !draw.is_visible {
+            continue;
+        }
+
         if let Some(text_glyphs) = text_pipeline.get_glyphs(&entity) {
             let position = global_transform.translation - (node.size / 2.0).extend(0.0);