Add a reminder to update latestEcmaScript() when adding a new language level.

PiperOrigin-RevId: 566829841

Author: brad4d

src/com/google/javascript/jscomp/parsing/Config.java

@@ -54,6 +54,8 @@ public enum LanguageMode {
     ECMASCRIPT_2019(FeatureSet.ES2019_MODULES),
     ECMASCRIPT_2020(FeatureSet.ES2020_MODULES),
     ECMASCRIPT_2021(FeatureSet.ES2021_MODULES),
+    // NOTE: When adding a new language level here, also update latestEcmaScript() below to return
+    // it.
     ES_NEXT(FeatureSet.ES_NEXT),
     UNSTABLE(FeatureSet.ES_UNSTABLE),
     UNSUPPORTED(FeatureSet.ES_UNSUPPORTED);