[clang-format] - [Feature Request] - Sort Forward Declarations

[CausticDream]

It looks like sort of forward declarations is a feature missing for clang-format.

[mydeveloperday]

Can you give good examples of what you are seeing and what you expect to see

[CausticDream]

The expected result is to sort the forward declaration by group. Here an example of Test.h and then Test.h after the sorting.

Test.h:

class ForwardDecl1;
class ForwardDecl0;

namespace Test
{
    class ForwardDecl3;
    class ForwardDecl2;
}

Test.h (after sorting):

class ForwardDecl0;
class ForwardDecl1;

namespace Test
{
    class ForwardDecl2;
    class ForwardDecl3;
}

[JanFellner]

Like this idea so i´m jumping in and voting for that idea :)