Update docs

packages/example/src/quickstart.ts

@@ -52,3 +52,35 @@ Effect.gen(function*() {
     // Mutations with the parent state are performed immutably by default
     // unless you use a specific mutable transform such as 'focusMutableField'
 })
+
+Effect.gen(function*() {
+    interface User {
+        readonly name: string
+        readonly age: DateTime.Utc
+    }
+
+    const ref = yield* SubscriptionRef.make<readonly User[]>([
+        { name: "Jean Dupont", age: yield* DateTime.make("03/25/1969") },
+        { name: "Juan Joya Borja", age: yield* DateTime.make("04/05/1956") },
+        { name: "Benzemonstre", age: yield* DateTime.make("06/12/2000") },
+    ])
+
+    //                  \/ Lens<User, NoSuchElementException, NoSuchElementException, never, never>
+    const benzemonstreLens = ref.pipe(
+        Lens.fromSubscriptionRef,
+
+        // Manually focus
+        Lens.mapEffect(
+            // Getter:
+            Array.get(2),
+            // Setter:
+            (a, b) => Array.replaceOption(a, 2, b),
+        //   ^ The current Lens value (readonly User[])
+        //      ^ The new focused value to push (User)
+        ),
+    )
+
+    // Both Array.get and Array.replaceOption return an Option
+    // When evaluated by the lens, Option<A> becomes Effect<A, NoSuchElementException>
+    // As you can see, this is automatically tracked by the Lens type
+})