Allow users to disable inline images on mobile data

**Is your feature request related to a problem? Please describe.**

We should minimise network access over data, and automatically showing inline images seems wasteful (you could, in theory, maliciously eat up someone's data plan).

**Describe the solution you'd like**

Allow me to disable inline images in chat when mobile data is enabled.

**Describe alternatives you've considered**

N/A

**Additional context**

N/A