add Hotshot-XL extension

[SpenserCai]

Info

Add Hotshot-XL extension:
Hotshot-XL: State-of-the-art AI text-to-GIF model trained to work alongside Stable Diffusion XL
https://github.com/hotshotco/Hotshot-XL
https://github.com/hotshotco/Hotshot-XL-Automatic1111

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.