Add a function to extract a specific object property

[Destroy666x]

As the title says, something like selectattr(array_of_objects, "property") similar to Jinja's selectattr (IIRC? unless I'm confusing with another engine).

So that you could:

• use statements like {{ join(selectattr(array_of_objects, "property"), ", ") }}
• simplify multiple loops on a single property