feature: Add version 2.8 to OtpVersion

Author: t2gran

Diff for: application/src/main/java/org/opentripplanner/standalone/config/framework/json/OtpVersion.java

@@ -12,7 +12,8 @@ public enum OtpVersion {
   V2_4("2.4"),
   V2_5("2.5"),
   V2_6("2.6"),
-  V2_7("2.7");
+  V2_7("2.7"),
+  V2_8("2.8");
 
   private final String text;