code: function addData (db, mime, source) {
    Object.keys(mime).forEach(function (key) {
      var data = mime[key]
      var type = key.toLowerCase()
      var obj = db[type] = db[type] || createTypeEntry(source)
  
      // add missing data
      setValue(obj, 'charset', data.charset)
      setValue(obj, 'compressible', data.compressible)
  
      // append new extensions
      appendExtensions(obj, data.extensions)
    })
  }
docs: Add mime data to the db, marked as a given source.