fix watcher mll file

Author: bobzhang

scripts/watcher.js

@@ -230,7 +230,7 @@ function exec() {
 
 function watch$1(dir) {
   return makeWatcher(dir, function (_, fileName) {
-              if (fileName.endsWith(".ml") || fileName.endsWith(".mli") || fileName.endsWith(".cppo") || fileName.endsWith(".js") || fileName === "Makefile" || fileName === "Makefile.shared") {
+              if (fileName.endsWith(".ml") || fileName.endsWith(".mli") || fileName.endsWith(".cppo") || fileName.endsWith(".js") || fileName === "Makefile" || fileName === "Makefile.shared" || fileName.endsWith(".mll")) {
                 return exec(/* () */0);
               } else {
                 return 0;