Update "Graphics" overview page

The Graphics overview page is very much geared towards Qt Quick and Qt Quick 3D.

Ideas for improvements:

• Move general QPA architecture a bit down (or in a sub-page)
• Mention capabilities of Qt 3D
• Mention capabilities of Qt Multimedia (video rendering)
• Mention capabilities of Qt Charts, Qt Data Visualization
• Mention image format support (in Qt Gui, Qt SVG, Qt ImageFormats, ...)
• Mention capabilities of Qt Lottie Animation

Proposed Structure (please augment!):

Graphics in Qt

2D Graphics

Shader Effects

Image Formats

Backends & Standard API's

QPA , OpenGL, Vulkan ...

Animations and Videos

Asset Conditioning