[Marketplace] Added additional context to listing name (#18758)

Author: shashban

content/developers/github-marketplace/writing-a-listing-description-for-your-app.md

@@ -24,7 +24,7 @@ Here are guidelines about the fields you'll need to fill out in the **Listing de
 
 #### Listing name
 
-Your app's name will appear on the [{% data variables.product.prodname_marketplace %} homepage](https://github.com/marketplace). The name is limited to 255 characters.
+Your listing's name will appear on the [{% data variables.product.prodname_marketplace %} homepage](https://github.com/marketplace). The name is limited to 255 characters and can be different from your app's name. Your listing cannot have the same name as an existing {% data variables.product.product_name %} user, unless the name is your own user or organization name. 
 
 #### Very short description