[request] Allow documentation at the end of the line

[correaa]

I know Mrdocs supports documentation at the end of the line in a very limited way (enums).
And I know it is mostly driven by LLVM limitations, but I wanted to state the need for this feature:

In order of priority (I don't think any of this is supported currently):

1. document typedef members, e.g.

template<class T> struct A {
   typedef T value_type;  //< document this
   using value_type = T;  //< document ths
}

2. document member variables

template<class T> class A {
   int size  //< document this
}

3. document function declarations

template<class T> class A {
   int size();  //< document this
}

4. document function definitions (useful for short function)

template<class T> class A {
   int size() const { return size_; }  //< document this
}