Add SVG component support

[Gujiassh]

Adds an initial SVG component implementation for React NodeGui.

What changed:

• Adds a <Svg> host component that serializes SVG-like child components to SVG XML and renders through QPixmap.loadFromData.
• Adds basic SVG nodes: <G>/<Group>, <Rect>, <Circle>, <Ellipse>, <Line>, <Polygon>, and <Path>.
• Exports the new components from the package entrypoint.
• Documents a minimal SVG usage example in the README.

This follows the initial MVP approach discussed in #31: generate an SVG string from React components and render it as an image. Prop updates regenerate the SVG image.

Validation:

• ./node_modules/.bin/tsc --noEmit --pretty false
• git diff --check

/claim #31

[Gujiassh]

Closing this as a duplicate of the newer SVG support lane in #389.

Issue #31 already points to that later PR as the active path for the same feature, so keeping this older branch open would just split review attention.