code: function injectAdditionalFunctions (funcs, additionalFunctions) {
    // Nothing to do if no additional function is given.
    if (no(additionalFunctions)) return
  
    /**
     * Validate and insert an additional function.
     */
  
    function injectAdditionalFunction (key) {
      var isAFunction = typeof additionalFunctions[key] === 'function'
  
      if (isAFunction) funcs[key] = additionalFunctions[key]
    }
  
    Object.keys(additionalFunctions)
      .forEach(injectAdditionalFunction)
  }
docs: Optionally add custom functions.
  
  @params {Object} funcs
  @params {Object} additionalFunctions