add js snippets

snippets/js2-mode/for.yasnippet

@@ -0,0 +1,9 @@
+# -*- mode: snippet -*-
+# name: for
+# key: for
+# --
+var ${1:i} = ${2:-1}, len = $3.length;
+
+for(; ++$1 < len;){
+  $4
+}