Add 1.3.2 changelog entry

CHANGELOG

@@ -1,3 +1,9 @@
+1.3.2
+- Swift 5.3 update (Xcode 12)
+- Bump target platform (iOS 9, macOS 10.12)
+- Allow CMAC with any Cipher
+- Remove CMAC key limit
+
 1.3.1
 - Fix tests
 - Swift 5.2 update