Add beforeInputUpdate doc

src/lib/components/Keyboard.ts

@@ -118,6 +118,7 @@ class SimpleKeyboard {
      * @property {function(input: string):string} onChange Executes the callback function on input change. Returns the current input’s string.
      * @property {function} onRender Executes the callback function every time simple-keyboard is rendered (e.g: when you change layouts).
      * @property {function} onInit Executes the callback function once simple-keyboard is rendered for the first time (on initialization).
+     * @property {function(keyboard: Keyboard):void} beforeInputUpdate Perform an action before any input change
      * @property {function(inputs: object):object} onChangeAll Executes the callback function on input change. Returns the input object with all defined inputs.
      * @property {boolean} useButtonTag Render buttons as a button element instead of a div element.
      * @property {boolean} disableCaretPositioning A prop to ensure characters are always be added/removed at the end of the string.