Update README

README.md

@@ -1,20 +1,46 @@
 # ProtobufKit
 
-[![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2FOpenSwiftUIProject%2FProtobufKit%2Fbadge%3Ftype%3Dswift-versions)](https://swiftpackageindex.com/OpenSwiftUIProject/ProtobufKit) [![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2FOpenSwiftUIProject%2FProtobufKit%2Fbadge%3Ftype%3Dplatforms)](https://swiftpackageindex.com/OpenSwiftUIProject/ProtobufKit)
+[![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2FOpenSwiftUIProject%2FProtobufKit%2Fbadge%3Ftype%3Dswift-versions)](https://swiftpackageindex.com/OpenSwiftUIProject/ProtobufKit) [![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2FOpenSwiftUIProject%2FProtobufKit%2Fbadge%3Ftype%3Dplatforms)](https://swiftpackageindex.com/OpenSwiftUIProject/ProtobufKit) [![codecov](https://codecov.io/gh/OpenSwiftUIProject/ProtobufKit/graph/badge.svg?token=VDKQVOP20I)](https://codecov.io/gh/OpenSwiftUIProject/ProtobufKit)
 
-ProtobufKit is a lightweight Swift library for working with Protocol Buffers.
+ProtobufKit is a lightweight[^1] replacement of [swift-protobuf](https://github.com/apple/swift-protobuf) for working with Protocol Buffers in Swift.
 
-It is cross-platform and compatible with SwiftUI's internal Protobuf implementation.
+## Overview
 
-## Getting Started Using ProtobufMessage
+ProtobufKit is cross-platform Swift package on Darwin platform (without OS version limitation) and Linux.[^2]
 
-In your `Package.swift` Swift Package Manager manifest, add the following dependency to your `dependencies` argument:
+| **Workflow** | **CI Status** |
+|-|:-|
+| **Compatibility Test** | [![Compatibility tests](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/compatibility_tests.yml/badge.svg)](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/compatibility_tests.yml) |
+| **macOS Unit Test** | [![macOS](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/macos.yml/badge.svg)](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/macos.yml) |
+| **iOS Unit Test** | [![iOS](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/ios.yml/badge.svg)](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/ios.yml) |
+| **Ubuntu 22.04 Unit Test** | [![Ubuntu](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/ubuntu.yml/badge.svg)](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/ubuntu.yml) |
+
+ProtobufKit is compatible with SwiftUI's internal Protobuf implementation so that you can use it to decode some internal binary data of SwiftUI (eg. ArchivedView).
+
+The core design of ProtobufKit is `ProtobufMessage` which is similar to `Codable` and easy to customize.
+
+```swift
+public protocol ProtobufEncodableMessage {
+    func encode(to encoder: inout ProtobufEncoder) throws
+}
+public protocol ProtobufDecodableMessage {
+    init(from decoder: inout ProtobufDecoder) throws
+}
+
+public typealias ProtobufMessage = ProtobufDecodableMessage & ProtobufEncodableMessage
+```
+
+You can also use it with Codable by conforming your message type to `CodaleByProtobuf` or annoate your message instance with `ProtobufCodable` propertyWrapper.
+
+## Getting Started
+
+In your `Package.swift` file, add the following dependency to your `dependencies` argument:
 
 ```swift
 .package(url: "https://github.com/OpenSwiftUIProject/ProtobufKit.git", from: "0.1.0"),
 ```
 
-Add the dependency to any targets you've declared in your manifest:
+Then add the dependency to any targets you've declared in your manifest:
 
 ```swift
 .target(
@@ -54,17 +80,9 @@ struct SimpleMessage: ProtobufMessage {
 Please see ProtobufKit [documentation site](https://swiftpackageindex.com/OpenSwiftUIProject/ProtobufKit/main/documentation/protobufkit)
 for more detailed information about the library.
 
-## Supported platforms
-
-The table below describes the current level of support that `ProtobufKit` has
-for various platforms:
+## Future work
 
-| **Workflow** | **CI Status** |
-|-|:-|
-| **Compatibility Test** | [![Compatibility tests](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/compatibility_tests.yml/badge.svg)](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/compatibility_tests.yml) |
-| **macOS Unit Test** | [![macOS](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/macos.yml/badge.svg)](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/macos.yml) |
-| **iOS Unit Test** | [![iOS](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/ios.yml/badge.svg)](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/ios.yml) |
-| **Ubuntu 22.04 Unit Test** | [![Ubuntu](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/ubuntu.yml/badge.svg)](https://github.com/OpenSwiftUIProject/ProtobufKit/actions/workflows/ubuntu.yml) |
+ProtobufKit does not have compiler build-in support like Codable`'s `Codable` protocol, so you have to write the encode and decode logic by yourself. This can be improved by future macro API support.
 
 ## License
 
@@ -83,3 +101,6 @@ See LICENSE file - MIT
     <img alt="Star History Chart" src="https://api.star-history.com/svg?repos=OpenSwiftUIProject/ProtobufKit&type=Date" />
   </picture>
 </a>
+
+[^1]: Under macOS + Build for profiling option, ProtobufKit's ProtobufKit.o is 142KB while [swift-protobuf](https://github.com/apple/swift-protobuf)'s SwiftProtobuf.o is 5.7MB
+[^2]: WASI support will be added in the future