Add OpenCV dependency for iOS (#47)

## Description
Pod: /~https://github.com/software-mansion-labs/opencv-rne

<!-- Provide a concise and descriptive summary of the changes
implemented in this PR. -->

### Type of change
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] Documentation update (improves or adds clarity to existing
documentation)

### Tested on
- [x] iOS
- [ ] Android

### Checklist
- [x] I have performed a self-review of my code
- [x] I have commented my code, particularly in hard-to-understand areas
- [x] I have updated the documentation accordingly
- [x] My changes generate no new warnings

react-native-executorch.podspec

@@ -16,5 +16,7 @@ Pod::Spec.new do |s|
   s.ios.vendored_frameworks = "ios/ExecutorchLib.xcframework"
   s.source_files = "ios/**/*.{h,m,mm}"
 
+  s.dependency "opencv-rne", "~> 0.1.0"
+
   install_modules_dependencies(s)
 end