Support lodepng for encoding PNGs

[orhun]

Is your feature request related to a problem? Please describe.

lodepng is a pure Rust PNG image decoder and encoder. Allows easy reading and writing of PNG files without any system dependencies.

We can support this crate as an alternative to the default PNG encoder.

Describe the solution you'd like

Add --lodepng flag to CLI/config and use lodepng encoder if it is set.

Describe alternatives you've considered -

Additional context

We can make lodepng default if it is more performant.