all: Release v0.33.0

Change-Id: Idf6a825c642b30d77a18df3397450b4513ae9c06
Reviewed-on: https://code-review.googlesource.com/c/35511
Reviewed-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jean de Klerk <deklerk@google.com>
diff --git a/CHANGES.md b/CHANGES.md
index e7533a8..18cbee4 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,5 +1,23 @@
 # Changes
 
+## v0.33.0
+
+- bttest:
+  - Add support for apply_label_transformer.
+- expr:
+  - Add expr library.
+- firestore:
+  - Support retrieval of missing documents.
+- kms:
+  - Add IAM methods.
+- pubsub:
+  - Clarify extension documentation.
+- scheduler:
+  - Add v1beta1 client.
+- vision:
+  - Add product search helper.
+  - Add new product search client.
+
 ## v0.32.0
 
 Note: This release is the last to support Go 1.6 and 1.8.