Format and link `func` definition to show in documentation

def format_ft_def(func, full_name:str=None)->str:
    "Format and link `func` definition to show in documentation"
    sig = inspect.signature(func)
    name = f'<code>{full_name or func.__name__}</code>'
    fmt_params = [format_param(param) for name,param
                  in sig.parameters.items() if name not in ('self','cls')]
    arg_str = f"({', '.join(fmt_params)})"
    if sig.return_annotation and (sig.return_annotation != sig.empty): arg_str += f" → {anno_repr(sig.return_annotation)}"
    if is_fastai_class(type(func)):        arg_str += f" :: {link_type(type(func))}"
    f_name = f"<code>class</code> {name}" if inspect.isclass(func) else name
    return f'{f_name}',f'{name}{arg_str}'