fix imports and make extra props optional

Author: chillitom

package.json

@@ -3,7 +3,7 @@
   "version": "1.0.1",
   "description": "A signature pad implementation in React",
   "main": "build/index.js",
-  "types": "src/index.d.ts", 
+  "types": "src/index.d.ts",
   "scripts": {
     "test": "webpack && npm pack",
     "start": "webpack-dev-server -d --inline --hot",

src/index.d.ts

@@ -1,3 +1,6 @@
+
+import * as React from 'react';
+
 // signature_pad's props 
 // (taken from https://github.com/szimek/signature_pad/blob/e2af461bca7ceb7cc5afb8349930908ca19f2f56/src/signature_pad.ts#L23)
 export interface IOptions {
@@ -15,8 +18,8 @@ export interface IOptions {
 
 // props specific to the React wrapper
 export interface SignatureCanvasProps extends IOptions {
-    canvasProps: any;
-    clearOnResize: boolean;
+    canvasProps?: any;
+    clearOnResize?: boolean;
 }
 
 export default class SignatureCanvas extends React.Component<SignatureCanvasProps> {}