Adding Umbraco Flavored Markdown for url-pickers and extract expression in general

[IbrahimMNada]

I will be sending you a pull request soon , if you have any thoughts please share

I want to add a feature that have been developing for the past few hours,
this feature simply displays the name of a url picker item at the block list property:

by simply adding an expression for the markdown like this :

it support changing the .name for any other custom value for example .url

[IbrahimMNada]

Pull Request : umbraco/Umbraco.CMS.Backoffice#2345