v1.1.0 of signwriting_flutter

Flutter utilities for SignWriting formats, tokenizer and visualizer. Changelog excerpt: - Accept SWU strings in signwritingToImage(auto-detected and converted) - Add signwritingsToImageto render and combine multiple signs (horizontal/vertical, centered) - trustBox: falsenow uses the tight box from signwritingBox(font-metric based), matching the Python reference - Re-export the pure signwritingutilities (incl. getSymbolSize, signwritingBox) for a single import - Fix documentation rendering (escape generic types in doc comments) - Require signwriting: ^1.4.0