Add support for PixivFE

[kamekku14]

Believe it or not, there's a privacy-respecting alternative front-end for Pixiv. It's called PixivFE.

Below here are the instances:

• https://pixivfe.exozy.me/ (Official)
• https://pixivfe.drgns.space/
• https://pixivfe.ducks.party/
• https://pixiv.perennialte.ch/
• https://pixivfe.darkness.services/
• https://pixivfe.thebunny.zone/