(feat): add on API method to rebind event handlers

- does the opposite of `off`
- replace internal usage with new `on` functionality as well

Author: Christopher Lee

src/index.js

@@ -35,8 +35,7 @@ export default class SignatureCanvas extends Component {
   componentDidMount () {
     this._ctx = this._canvas.getContext("2d");
 
-    this._handleMouseEvents();
-    this._handleTouchEvents();
+    this.on()
     this._resizeCanvas();
     this.clear()
   }
@@ -142,6 +141,11 @@ export default class SignatureCanvas extends Component {
     document.addEventListener('touchend', this._handleTouchEnd)
   }
 
+  on = () => {
+    this._handleMouseEvents()
+    this._handleTouchEvents()
+  }
+
   off = () => {
     this._canvas.removeEventListener('mousedown', this._handleMouseDown)
     this._canvas.removeEventListener('mousemove', this._handleMouseMove)