added function to convert images to .mif file format

[grnarayanan]

Solves Issue #5 and adds support for producing output files in .mif format in addition.

Added convert_to_mif() function that takes in input image data and creates a string to be written to output file formatted for a mif file, specifying fields such as width, depth, radix, and content. Documented with Napoleon style doc string.

Added test case in test.py to verify functionality.

[WillGreen]

Hello,

Thank you for adding MIF support to img2fmem. Could you update img2fmem/README.md to include basic info on MIF support and how to run your test?

TIA, Will