Add new value "es2018" for module kind

src/compiler/commandLineParser.ts

@@ -109,8 +109,9 @@ namespace ts {
                 "umd": ModuleKind.UMD,
                 "es6": ModuleKind.ES2015,
                 "es2015": ModuleKind.ES2015,
+                "es2018": ModuleKind.ES2018
             }),
-            description: Diagnostics.Specify_module_code_generation_Colon_commonjs_amd_system_umd_or_es2015,
+            description: Diagnostics.Specify_module_code_generation_Colon_commonjs_amd_system_umd_es2015_or_es2018,
             paramType: Diagnostics.KIND,
         },
         {

src/compiler/diagnosticMessages.json

@@ -2569,7 +2569,7 @@
         "category": "Message",
         "code": 6015
     },
-    "Specify module code generation: 'commonjs', 'amd', 'system', 'umd' or 'es2015'.": {
+    "Specify module code generation: 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'es2018'.": {
         "category": "Message",
         "code": 6016
     },

src/compiler/types.ts

@@ -3426,6 +3426,7 @@ namespace ts {
         UMD = 3,
         System = 4,
         ES2015 = 5,
+        ES2018 = 6
     }
 
     export const enum JsxEmit {