Add README.

Author: ilopX

patterns/iterator/word_iterator/README.md

@@ -0,0 +1,47 @@
+# Iterator pattern
+Iterator is a behavioral design pattern that lets you traverse elements of a collection without
+exposing its underlying representation (list, stack, tree, etc.).
+
+Tutorial: [here](https://refactoring.guru/design-patterns/iterator).
+
+### Client code:
+```dart
+void main() {
+  final text = Text(
+    'Iterator is a behavioral design pattern that lets you traverse elements '
+        'of a collection without exposing its underlying representation '
+        '(list, stack, tree, etc.).',
+  );
+
+  for (final s in text) {
+    print(s);
+  }
+}
+```
+
+**Output:**
+```
+Iterator
+is
+a
+behavioral
+design
+pattern
+that
+lets
+you
+traverse
+elements
+of
+a
+collection
+without
+exposing
+its
+underlying
+representation
+list
+stack
+tree
+etc
+```