Some fediverse platform icons
## Describe the requested icon(s)
I noticed that phosphor added icons for the fediverse and Mastodon. I take this as a sign of interest in including fedi software, and have a couple of suggestions for other fediverse software icons to include. These will be useful for collections of social media links. 

### Platforms
- [Lemmy](https://join-lemmy.org/)
- [Peertube](https://joinpeertube.org/)
- [Pixelfed](https://pixelfed.org/)
- [Misskey](https://misskey-hub.net/en/)
- [Firefish](https://joinfirefish.org/)
- [Pleroma](https://pleroma.social/)
- [Akkoma](https://akkoma.social/)
- [Friendica](https://friendi.ca/)

## References

### Lemmy
![Lemmy logo](https://github.com/phosphor-icons/homepage/assets/28871516/96a719fa-9c79-413c-805a-d1837c3e50ef)

### Peertube
![Peertube logo](https://github.com/phosphor-icons/homepage/assets/28871516/13970710-e4e5-4a62-b672-a7e4e93e3ed7)

### Pixelfed
![Pixelfed logo](https://github.com/phosphor-icons/homepage/assets/28871516/94fac4ff-360d-4f32-90be-774b2b67c6a4)

### Misskey
![Misskey logo](https://github.com/phosphor-icons/homepage/assets/28871516/2a3e5d91-7bce-4544-992d-6d6324cf8ab1)

### Firefish
![Firefish logo](https://github.com/phosphor-icons/homepage/assets/28871516/78a08e39-8b79-4bf4-9ada-d014034a1db7)

### Pleroma
![Pleroma logo](https://github.com/phosphor-icons/homepage/assets/28871516/3f15fa40-e0fb-4bdc-9af1-ca45d6a7e42b)

### Akkoma
![Akkoma logo](https://github.com/phosphor-icons/homepage/assets/28871516/72cd5761-0c40-4e58-9b80-9c1a6644efe8)

### Friendica
![Friendica logo](https://github.com/phosphor-icons/homepage/assets/28871516/8c177f6e-4b87-4389-931e-d5b2fdfc2ef5)

## Additional context

I'm a bit biased towards Lemmy being included since I'm one of its maintainers.

I'm also a big fan of this icon library. [I'm even using it in Lemmy's UI rewrite](https://github.com/LemmyNet/lemmy-ui-leptos/blob/main/public/icons.svg?short_path=b015b0a)