Upgrade to egui 0.31 (#234)

### Checklist

* [x] I have read the [Contributor Guide](../CONTRIBUTING.md)
* [x] I have read and agree to the [Code of
Conduct](../CODE_OF_CONDUCT.md)
* [x] I have added a description of my changes and why I'd like them
included in the section below

### Description of Changes

Upgraded to egui 0.30.

### Related Issues

Fixes #233

Author: tedsteen