Add support for Inpainting about diffusers-rs

[LaurentMazare]

I've added an inpainting pipeline/example and it seems to work fine on the examples that I've tried. You can see some sample in the main readme.
Note that this requires a different weight files for the unet.

[makeecat]

The example of inpainting needs to be fixed from

cargo run --example stable-diffusion-inpaint --input-image sd_input.png --mask-image sd_mask.png

to

cargo run --example stable-diffusion-inpaint --features clap -- --input-image sd_input.png --mask-image sd_mask.png

[LaurentMazare]

The readme example should be fixed now, thanks for reporting.