Raster (PNG) and PDF backends for rpic.
These consume the SVG produced by rpic-core and convert it with pure-Rust
libraries (no system dependencies), keeping rpic-core itself
dependency-free and WASM-friendly.
- PNG: parse the SVG with
usvg, rasterize withresvg/tiny-skia. - PDF: parse with svg2pdf's
usvg, convert withsvg2pdf.
Both load system fonts so attached text renders.