Update readme add documentation

Author: TayGov

src/backend/README.md

@@ -33,3 +33,7 @@ Run
 ```
 mvn -f src/backend/pom.xml versions:set -DartifactId=*  -DgroupId=*
 ```
+
+## caching
+
+Currently lookups are cached using redis. In the event of a code table change redis should be restarted. Check the api for activity beore doing so.