add dll support

[ZhangMengRou]

Both exe and dll are PE files.
[]byte{0x4D, 0x5A} is PE's magic number

Differentiation:

> IMAGE_FILE_DLL
> 0x2000
> The  image  is  a  DLL  file.  While  it  is  an  executable  file,  it  cannot  be  run  directly

Thanks.

Source:
https://docs.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-image_file_header?redirectedfrom=MSDN
https://docs.microsoft.com/en-us/previous-versions/ms809762(v=msdn.10)?redirectedfrom=MSDN

[LordNoteworthy]

would be nice to get this one merged, though I would like to have a unified type called PE, and then additional input like dll, exe or driver would be extra information.