Can packed structures be supported?

I noticed that packed structures are not supported, while it is not mentioned in documentation.

For example:

```c++
struct __attribute__ ((packed)) A
{
int x;
int z;
bool y;
};
```

The error message is following:

```
static_assert(sizeof(U) == sizeof(S), "====================> Boost.PFR: Member sequence does not indicate correct size for struct type! Maybe the user-provided type is not a SimpleAggregate?");
~~~~~~~~~~^~~~~~~~~~~~
```
Link: https://godbolt.org/z/Exo16Mods

However, the class should be an Aggregate, as

> _An aggregate is an array or a class (clause 9) with no user-declared constructors (12.1), no private or protected non-static data members (clause 11), no base classes (clause 10), and no virtual functions (10.3)._

Is there a technical obstacle on adding packed structures?