Adding OpenHTJ2K as one of the codecs

[osamu620]

Hi!
How about adding (OpenHTJ2K https://github.com/osamu620/OpenHTJ2K) as one of the codecs?
It is not as fast as Kakadu, but it performs as well as OpenJPH and the decoder is compliant with the ISO/IEC 15444-4 spec.

FYI:
In OpenHTJ2K,

• block coding is multi-threaded.
• FDWT/IDWT and some parts of HT block coding are vectorized for both Intel and ARM CPUs.

Thanks for your consideration in advance!

[osamu620]

PR #9 to add open_htj2k support.