a note about the total max length of the text inside v2

Author: NervN

guide/CodeReferences/ref.v2_components.md

@@ -17,6 +17,7 @@ You can use {container:data} to send a message with v2 component
 ```
 * total number of components (i.e container, text...) cannot exceed 40 in the whole message
 * container can hold up to 40 components (i.e text, gallery,...) as max.
+* total text content length in the message should be at max of 4000
 
 #### section structure
 section allow you to add a text + image + button together in inside the container, a section should contain at least one text and one accessory (image or button).