Add optional parameters to limit the maximum dimensions ---max-width, --max-height

[totoestcontent]

Some svgs have a huge viewbox and I would need to limit the size of the png produced. The current settings (-w and -h) allow this if the image is larger than the given values. If the image is smaller then it will be enlarged. The idea is therefore not to exceed a given dimension (optional).

I made the changes and created a git patch.

Be indulgent, it's the first time I do Rust ;-) So you can do much better, but if it can make your job easier, I'd be happy ;-)

add_max_width_height.patch