[Feature Request]: Comply with Flathub Quality checks

[tsunamistate]

Feature Type

Quality of Life

Describe

Need to comply with Flathub Quality checks on https://flathub.org/apps/org.diasurgical.DevilutionX
Quote from Flathub docs: The following guidelines are not required for submission to Flathub, but are best practices we recommend and consider for curation and promotion. These guidelines are designed to help your app and Flathub itself appear in the best light to users.

Currently failing:

• Branding
  • Has primary branding colours: I'll consult in Flathub issue what good branding colours would be
• App icon
  • Doesn't fill too much or too little of the canvas: I don't get it
  • Good contrast on dark backgrounds: Don't get this either
• App name
  • No weird formatting, punctuation, lowercase, etc.: Should make the case that this is an established brand, and to differentiate from Devilution
• Summary
  • Understandable for a non-technical person: Probably change "source port" to "build", like in Github description?