[bugfix] Configure `node_modules` location for scratchpad.

examples/scratchpad.html

@@ -32,6 +32,7 @@
     var jscoq_opts = {
         backend: sp.get('backend'),
         subproc: sp.has('app'),
+        node_modules_path: '../node_modules/',
         file_dialog: true,
         implicit_libs: true,
         editor: { mode: { 'company-coq': true }, theme: editor_theme },