Add starts to a channel guide

Author: phausler

Guides/Channel.md

@@ -0,0 +1,50 @@
+# Channel
+
+* Author(s): [Philippe Hausler](https://github.com/phausler)
+
+[
+[Source](https://github.com/apple/swift-async-algorithms/blob/main/Sources/AsyncAlgorithms/AsyncChannel.swift),
+[Source](https://github.com/apple/swift-async-algorithms/blob/main/Sources/AsyncAlgorithms/AsyncThrowingChannel.swift) |
+[Tests](https://github.com/apple/swift-async-algorithms/blob/main/Tests/AsyncAlgorithmsTests/TestChannel.swift)
+]
+
+## Introduction
+
+## Proposed Solution
+
+```swift
+public final class AsyncChannel<Element: Sendable>: AsyncSequence, Sendable {
+  public struct Iterator: AsyncIteratorProtocol, Sendable {
+    public mutating func next() async -> Element?
+  }
+  
+  public init(_ elementType: Element.Type = Element.self)
+  
+  public func send(_ element: Element) async
+  public func finish() async
+  
+  public func makeAsyncIterator() -> Iterator
+}
+
+public final class AsyncThrowingChannel<Element: Sendable, Failure: Error>: AsyncSequence, Sendable {
+  public struct Iterator: AsyncIteratorProtocol, Sendable {
+    public mutating func next() async throws -> Element?
+  }
+  
+  public init(_ elementType: Element.Type = Element.self)
+  
+  public func send(_ element: Element) async
+  public func fail(_ error: Error) async where Failure == Error
+  public func finish() async
+  
+  public func makeAsyncIterator() -> Iterator
+}
+```
+
+## Detailed Design
+
+## Alternatives Considered
+
+It was consider to use the naming heritage of "subject".
+
+## Credits/Inspiration