Add documentations for controlnet_conditioning_scale_map, alignment_ratio and alpha_weight

In utils/stable_diffusion_controlnet_inpaint.py, StableDiffusionControlNetInpaintMixingPipeline, three newly added params are not documented.

• controlnet_conditioning_scale_map
• alignment_ratio
• alpha_weight

• controlnet_conditioning_scale_map is a 2D tensor map for pixel-wise control_scale.
• alpha_weight is the mixing strength with original image during denoising.
• alignment_ratio is the control the number of steps to fill the original image during inpainting.

Will be added. Thanks for your notice.