feat: support canada region (#113)

https://coveord.atlassian.net/browse/KIT-2900

Author: y-lakhdar

src/main/java/com/coveo/pushapiclient/Region.java

@@ -4,7 +4,8 @@
 public enum Region {
   US("us"),
   EU("eu"),
-  AU("au");
+  AU("au"),
+  CA("ca");
 
   private String value;