Add setlocal suffixesadd+=.js to ftplugin

This suffixesadd setting helps Vim understand text that references a
path and does not contain the .js extension, as is often the case in
CommonJS style require statements. This improves motions like `gf` and
commands like `:find`. More information:

  http://usevim.com/2013/01/04/vim101-jumping/

Author: lencioni

ftplugin/javascript.vim

@@ -0,0 +1 @@
+setlocal suffixesadd+=.js