[release] Add release notes for 2.18.4

Change-Id: If8ee0291c6baacf8d8c69f73f90ab4602fa58ab1
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/266940
Reviewed-by: Michael Thomsen <mit@google.com>

CHANGELOG.md

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0c4fb4f..1871313 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -227,6 +227,13 @@
 - **Breaking change** [49473](https://github.com/dart-lang/sdk/issues/49473):
   dart2js no longer supports HTTP URIs as inputs.
 
+## 2.18.4 - 2022-11-02
+
+This is a patch release that fixes crashes during hot reload
+(issue [flutter/flutter#113540][]).
+
+[flutter/flutter#113540]: https://github.com/flutter/flutter/issues/113540
+
 ## 2.18.3 - 2022-10-19
 
 This is a patch release that fixes a regression in code coverage computation