Embedded argument support for examples in libdoc

When writing examples using libdoc, you typically want to use concrete examples with clarifying arguments. However, when you do that using embedded arguments, libdoc can no longer link the keyword to its definition.

Consider this snippet. The keyword from the example is not being linked:

@keyword("Shout ${n} cheers for")
def hurray(self, n:int, person:str):
    """Cheer them on as much as you like!
    
    Example:
    | `Shout 3 cheers for` | Robot |
    """

Start by reproducing the supplied Python example through the libdoc entry point, focusing on the embedded argument in Shout 3 cheers for. Trace how the example keyword is resolved against the @keyword definition. Done means libdoc links the embedded-argument example to its keyword definition.