doc: add example.

Author: jaywcjlove

core/README.md

@@ -128,6 +128,53 @@ export default function App() {
 }
 ```
 
+## Stroke
+
+```jsx mdx:preview
+import React, { useRef, useEffect } from "react";
+import Signature from '@uiw/react-signature';
+
+const points = {
+  "path-1": [[83.52734375,63.6015625],[83.22265625,64.02734375],[81.86328125,66.0390625],[78.69140625,70.90625],[72.76171875,80.44140625],[67.01171875,91.421875],[64.5390625,98.19921875],[63.83203125,101.25390625],[63.640625,102.5078125],[63.62109375,102.7109375],[63.96484375,102.22265625],[64.890625,100.87890625],[66.3671875,98.515625]],
+  "path-2": [[116.5546875,65.8359375],[117.3125,65.8359375],[119.23046875,65.90625],[122.078125,66.39453125],[125.44140625,67.51171875],[128.33203125,69.2421875],[130.6484375,71.53515625],[131.94140625,73.6796875],[132.28125,75.65234375],[132.0625,77.5],[130.33203125,79.78125],[126.4921875,83.24609375],[120.9375,87.5234375],[114.859375,91.13671875],[108.09765625,93.66796875],[101.8359375,94.7734375],[96.26953125,94.7734375],[92.23828125,94.90625],[89.94921875,94.96484375],[88.234375,95.04296875],[88.03515625,95.08984375],[89.6015625,95.4296875],[94.75,96.640625],[107.55859375,98.640625],[123.6171875,100.09375],[135.5546875,100.734375],[141.140625,101.03515625],[142.2578125,101.08984375]]
+}
+
+export default function App() {
+  return (
+    <Signature
+      defaultPoints={points}
+      options={{
+        size: 6,
+      }}
+      renderPath={(path, keyName) => {
+          return (
+            <>
+              <path
+                d={path}
+                strokeWidth="3"
+                stroke="blue"
+                fill="transparent"
+                strokeLinejoin="round"
+                strokeLinecap="round"
+                pointerEvents="all"
+              />
+              <path
+                d={path}
+                strokeWidth="0"
+                stroke="transparent"
+                fill="#dadada"
+                strokeLinejoin="round"
+                strokeLinecap="round"
+                pointerEvents="all"
+              />
+            </>
+          )
+      }}
+    />
+  );
+}
+```
+
 ## Props
 
 ```ts