Not all animated stickers animate

### Steps to reproduce

1. Send a sticker of animated image from a client that supports it.
2. View the sticker from within Element X.

### Outcome

#### What did you expect?
The sticker should animate.

#### What happened instead?
It is rendered as a static image.

#### What might be the cause?
It's probably that Element X uses the mimetype included in the event to determine whether to animate it or not. It may expect specifically `image/gif`, though `image/png` can refer to an [Animated PNG](https://en.wikipedia.org/wiki/APNG).

### Your phone model

_No response_

### Operating system version

Android 13

### Application version and app store

Element X version 0.5.1

### Homeserver

Synapse 1.114.0

### Will you send logs?

No

### Are you willing to provide a PR?

No