Allow font selection for profile icons

# Allow font selection for profile icons
As it stands right now, profile icons can either be a valid image file or a valid Unicode character (typically Emoji). I was playing around with alternatives, and it looks like that any character in the Segoe font family will play nice, even if updated on a Windows 10 machine to Segoe Fluent. I think that adding the ability to select an arbitrary font for text-based icons would open some doors for people who would prefer to use something like [Material](https://github.com/google/material-design-icons) or [Nerd Fonts](https://github.com/ryanoasis/nerd-fonts) for a consistent style and wider range of available icons. It would also have the benefit of scaling on screens better than your average PNG.

Here is a slapdash mockup of what I am describing:

Start by locating the existing profile-icon handling and the path that renders Unicode characters versus image files. Define how an arbitrary font would be selected and represented, then check the mockup and issue requirements against the existing profile-icon behavior. Done means text-based icons can use a selected font while preserving current image and Unicode options.

Written by the indexing model from the issue text.