Update security policy

Add v0.3

SECURITY.md

@@ -7,7 +7,8 @@ currently being supported with security updates.
 
 | Version | Supported          |
 | ------- | ------------------ |
-| 0.2.x   | :white_check_mark: |
+| 0.3.x   | :white_check_mark: |
+| 0.2.x   | :x: |
 | 0.1.x   | :x:                |
 
 ## Reporting a Vulnerability