Add themed image effect

[diluculo]

This commit is a solution to #244.

• Custom HLSL file, ThemedImage.fx, was compiled with the Shazzam Shader Editor.
• This pixel shader effect was applied to the icons in toolbar, menu, and windows title bar.

[EchterAgo]

I see this uses BindingProxy which does not mention any license on the blog post. @thomaslevesque is it OK to include your code? Gemini is licensed under either the Apache License Version 2.0 or the Microsoft Public License (Ms-PL): https://github.com/tgjones/gemini/blob/master/LICENCE.txt

[thomaslevesque]

@EchterAgo yes, it's fine. Thanks for asking.

[diluculo]

Rebased.