Fix changelog and version (#303)

The added feature was not merged before the package publish.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index f5b9279..7f56df0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.19.0-wip
+
+- Adds `shuffled` to `IterableExtension`.
+
 ## 1.18.0
 
 - `CanonicalizedMap`:
@@ -6,7 +10,6 @@
     - `toMap`: creates a `Map<K,V>` (with the original key values).
     - `toMapOfCanonicalKeys`: creates a `Map<C,V>` (with the canonicalized keys).
 - Fixes bugs in `ListSlice.slice` and `ListExtensions.slice`.
-- Adds `shuffled` to `IterableExtension`.
 - Update to `package:lints` 2.0.1.
 
 ## 1.17.2
diff --git a/pubspec.yaml b/pubspec.yaml
index c6a48f5..b7c9919 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: collection
-version: 1.18.0
+version: 1.19.0-wip
 description: >-
   Collections and utilities functions and classes related to collections.
 repository: https://github.com/dart-lang/collection