VAE BlessUp: Fix VAE brightness and contrast on-the-fly

[catboxanon]

New extension shared here that supports fixing VAE brightness and contrast on-the-fly in the web UI: https://git.mmaker.moe/mmaker/sd-webui-vae-blessup

Example (0.0 and 1.0 are the default values for brightness and contrast respectively):

Related: https://github.com/sALTaccount/VAE-BlessUp

Note: Currently there's an issue when using this extension or the provided VAEs with img2img/hires fix, track the issue here: saltacc/VAE-BlessUp#1