Implements the proposal detailed at
josch/img2pdf#112 (comment)
This is a limited implementation of JBIG2, which can be extended to
support multiple pages, symbol tables, and other features of the format
in the future.
To test, I included a test fixture. You can also download 042.bmp (the same
one as @josch already downloaded in josch/img2pdf#112 (comment)
from https://git.ghostscript.com/?p=tests.git;a=blob_plain;f=jbig2/042.bmp;hb=HEAD
and run the following command:
jbig2 042.bmp | img2pdf > 042.pdf
This results in a small PDF, just as @josch originally found in the
comment mentioned above.
This is my first contribution to this repository so let me know if
something else is needed. Thanks for a great library!
