add sd-webui-vae-tools

[light-and-ray]

Info

https://github.com/light-and-ray/sd-webui-vae-tools

Adds a postprocessing script inside Extras tab that allows you to use VAE models on images: encode, decode, encode+decode. It allows you exploring vae compression artifacts, how different vae models work together, and storing images in encoded vae form as a funny cipher

Checklist:

• I have read the Readme.md
• The description is written in English.
• The index.json and extension_template.json have not been modified.
• The entry is placed in the extensions directory with the .json file extension.