[feat] add image splitter feature

[thangdevalone]

What changed

• added a new splitImage() API that slices an image into a configurable rows x columns grid
• implemented native split processing on Android and iOS while keeping original pixel dimensions and exposing per-tile output metadata
• regenerated Nitro bridge files and updated the example app plus both READMEs to demonstrate the new feature

Why

• the toolkit was missing a native image splitting workflow for producing multiple output images from one source asset

Impact

• consumers can now generate tile images directly from React Native without building custom JS/native glue
• the example app now includes controls to test image splitting and preview the generated tiles

Validation

• ran yarn codegen
• ran yarn typecheck
• ran npx tsc --noEmit -p example\\tsconfig.json
• yarn lint still fails due to existing repo-wide CRLF/Prettier line-ending issues, not from this feature