[Feature] Custom expansion icons

[fernandoesra]

Option to add custom icons to custom expansions. Not just shortened versions of the name.

Now:

It would be great if the custom icon could be displayed there. And while using the app, when it tells you to "Find tile X (expansion icon)," the icon should be drawn.

Example of an icon in tiles:

[Quantumrunner]

Icons for custom content packs can now be optionally defined (see documentation here: https://github.com/NPBruce/valkyrie/wiki/Create-Custom-Content-Packs#contentpack-section).

Furthermore there is new dialog added now that shows required expansions when clicking at the icons:

This is all available in test release https://github.com/NPBruce/valkyrie/releases/tag/3.20 in a few minutes.

[Quantumrunner]

Implemented in release https://github.com/NPBruce/valkyrie/releases/tag/3.20-major