[FEATURE] macOS support

[mrousavy]

Problem

Currently there is no support for react-native-macos.

Solution

A macOS implementation.

1. Create macos/ folder
2. Create Xcode Project
3. Export React Methods
4. Add Blurhash Encoder/Decoder
   1. Use Swift Encoder/Decoder
   2. Use C Encoder/Decoder and interop

[mrousavy]

Resources:

• react-native-macos getting started
• react-native-webview for example usage with iOS code sharing
• reactnative.directory filtered by libraries with macos support

[mrousavy]

Progress is on the support-macos branch. ⌛