jpg loader: support static jpeg loader using richgel999

jpg loader: support static jpeg loader using richgel999

Adds an alternative static jpg loader.

The jpg loader copied the jpeg decoding implementation from this open-source
repo: https://github.com/richgel999/jpeg-compressor
That opensource has the public-domain license, it doesn't have any restriction
of the copy.

note: jpgd.cpp is modified version (changed decompress_jpeg_image_from_stream)
for returning BGRA