Add SVG component support with runtime fixes

[bpc-oss]

Summary

This PR adds SVG component support to react-nodegui using QSvgWidget, and includes the runtime fixes needed to make the feature work reliably.

It covers:

• Svg root component plus exported helpers like Rect, Circle, Path, and SvgText
• inline SVG tree serialization
• src, content, and buffer loading paths
• mixed text / tspan handling inside SVG text nodes
• safe child move/reorder behavior in SVG trees
• a repo-local acceptance command: npm run verify:svg

Fixes #31.

Why this PR

There are already related attempts in #387, #388, and #389. Compared with those branches, this version also fixes the runtime issues that blocked a clean handoff:

• fixes unbound createInstance behavior for nested SVG elements
• removes the private @nodegui/nodegui/dist/... dependency
• adds SVG-specific text update handling in the reconciler
• fixes reorder semantics so moved SVG children are not duplicated
• codifies acceptance coverage in-repo instead of relying only on ad hoc smoke commands

Verification

Ran locally:

• npm run build
• npm run verify:svg

npm run verify:svg covers:

• root import smoke
• README helper shapes
• lowercase rect
• SvgText
• content / buffer / src
• adjacent text serialization
• mixed tspan serialization
• mixed text update after mount
• reorder / move behavior

Notes

• SVG text should use SvgText rather than the existing host Text component.
• Verification is now repo-local and repeatable, though it is still an acceptance harness rather than a full unit/integration test suite.