Add support for the decoding of jpeg2000

[CharlieS1103]

Note: I'm not that experienced in rust (this is essentially my first real project in the language) so let me know if I did anything wrong. Also, I believe that the test case is in the jp2000, however, it is different than all the other test cases, I simply have no idea how to create my own .icns file containing a jp2k checkmark.