Updated to add things to keep in mind. (#22037)

* Updated to add things to keep in mind.

Added things to keep in mind so people don't mess up and missuse them and then ask themselves what's wrong ( more like a extra check for people

* fixed formatting

guide/english/bootstrap/icons/index.md

@@ -63,6 +63,16 @@ _Note: Do not include the dot in the HTML Class Attribute, referring to the clas
 
 _Note: Bootstrap's Glyphicons icon is not avalable on bootstrap V4_
 
+### Things to keep in mind
+
+**Don't mix with other components**
+
+Icon classes cannot be directly combined with other components. They should not be used along with other classes on the same element. Instead, add a nested `<span>` and apply the icon classes to the `<span>`.
+
+**Only use icons on empty elements**
+
+Icon classes should only be used on elements that contain no text content and have no child elements.
+
 ### More Information:
 
 - [Bootstrap Glyphicons Icons Doc](https://getbootstrap.com/docs/3.3/components/#glyphicons)