Creation of a UI system for IceShard.

[Dandielo]

Is your feature request related to a problem? Please describe.
Currently we can only define Developer UI's that are created using the ImGUI library. However, this is not idea when it comes to a final Game UI. It also does not define any data representation and is only available in code.

Describe the solution you'd like
After some reading, talking, and searching for existing solutions I've found the best thing would be to base it on an XML document. This is the best approach due to several things:

• It's a common language / tool to represent UI data already (XAML, HTML, Unity, Chrome Engine, etc...)
• It's already quite defined and has lots of tools and libraries that can help with writing and reading these.

Describe alternatives you've considered
Alternatively, we could use JSon, Yaml or Lua, however solutions that go this way are sparse and the formats are less popular for UI than XML.

Additional context
A sample of how a UI file could look like:
https://gist.github.com/Dandielo/9bd4021bda19358a90f408334d817189

[Dandielo]

UI Xaml based library:
https://www.noesisengine.com/?fbclid=IwAR1WzzQjND8zXrld8Skjuea81XXe9YrRAiSvX33nXbtob7_8HWC18BkbNFk#goto-home-main-features