Add config for toobusy middleware

With very low CPU frequency or bad IO situation, as well as not-loaded
JS CodiMD happens to present unneeded "I'm busy"-messages to users.

This patch allows to configure the lag. The default is taken from the
libray but set in our own default configs.

Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>

lib/web/middleware/tooBusy.js

@@ -2,7 +2,11 @@
 
 const toobusy = require('toobusy-js')
 
+
 const response = require('../../response')
+const config = require('../../config')
+
+toobusy.maxLag(config.tooBusyLag)
 
 module.exports = function (req, res, next) {
   if (toobusy()) {