Update README.md

Author: muukii

README.md

@@ -1,23 +1,46 @@
-# IndexedForEach
+# IndexedCollection
+
+A wrapper collection that provides items with its index using underlying collection without allocation.
 
 ## Motivation
-The purpose of using IndexedForEach is to read array's element and its index in safe way.  
-As using `.enumerated()` is unsafe way because of the index does not always start from 0.
+
+In SwiftUI, we might use these following technique for using index in `ForEach`.
+
+```swift
+ForEach(Array(array.enumerated()), id: \.offset) { ... }
+```
+
+```swift
+ForEach(zip(array.indices, array), id: \.0) { ... } 
+```
+
+There is downside like followings:
+- Creating new buffer by making new collection
+- `enumerated` provides index from 0 so that makes wrong access on using slice.
 
 ## Usage
 
+```swift
+#Preview {
+  VStack {
+    ForEach.init(IndexedCollection([1, 2, 3, 4, 5]), id: \.index, content: { e in
+      Text("\(e.index): \(e.value)")
+    })
+  }
+}
 ```
-import SwiftUI
-
-struct ContentView: View {
-    let numbers = [1, 2, 3]
-    
-    var body: some View {
-        VStack {
-            IndexedForEach(numbers) { index, element in
-                Text("\(index): \(element)")
-            }
-        }
-    }
+
+```swift
+struct IdentifiableItem: Identifiable {
+  let id: String
+  let value: UUID = .init()
+}
+
+#Preview {
+  VStack {
+    ForEach.init(IndexedCollection(["a", "b", "c", "d", "e"].map(IdentifiableItem.init(id:))), content: { e in
+      Text("\(e.index): \(e.value)")
+    })
+  }
 }
 ```