Resize image before saving to file

[sloganking]

Currently resizing is done on already saved PNG images. This is wasteful as we waste time encoding and decoding PNG images as an intermediate step. Ideally we should resize images right after they are created while they are still in memory.

Requirements:

• #7
• [ ] Convert ImageBuffer<Rgb<u8>, MmapMut> to DynamicImage so we can run resize.

[sloganking]

Or we could build a resize function directly into codevis::render