Add English explanation for clone operation

[jidanni]

The document says: You can save attributes from an item and restore these attributes to an other item (with the same type)

However with just a fast-running looping video, an English explanation is also required.

[Binnette]

Hi @jidanni. Thank for your excellent remark. I added an explanation as asked (c1983db4e8f9f63825064640dcb31df92d11b668)