Fix up error message to be more descriptive

Author: Vishwac Sena Kannan

packages/luis/src/parser/lufile/parseFileContents.js

@@ -554,7 +554,8 @@ const parseAndHandleEntityV2 = function (parsedContent, luResource, log, locale)
             let entityName = entity.Name.replace(/^[\'\"]|[\'\"]$/g, "");
             let entityType = !entity.Type ? getEntityType(entity.Name, entities) : entity.Type;
             if (!entityType) {
-                let errorMsg = `No type definition found for entity "${entityName}"`;
+                
+                let errorMsg = `No type definition found for entity "${entityName}". Supported types are ${Object.values(EntityTypeEnum).join(', ')}. Note: Type names are case sensitive.`;
                 let error = BuildDiagnostic({
                     message: errorMsg,
                     context: entity.ParseTree.newEntityLine()