Update README.md

When I tried running the sample, it shows me an error. After adding "this." to "resultsContainer, the error was cleared.

Author: Ben-Dynamsoft

hello-world/react/README.md

@@ -173,10 +173,10 @@ class VideoCapture extends React.Component {
       ) => {
         if (!result.barcodeResultItems.length) return;
 
-        resultsContainer.current!.textContent = '';
+        this.resultsContainer.current!.textContent = '';
         console.log(result);
         for (let item of result.barcodeResultItems) {
-          resultsContainer.current!.append(
+          this.resultsContainer.current!.append(
             `${item.formatString}: ${item.text}`,
             document.createElement('br'),
             document.createElement('hr'),
@@ -527,4 +527,4 @@ See the section about [deployment](https://facebook.github.io/create-react-app/d
 
 ## Support
 
-If you have any questions, feel free to [contact Dynamsoft support](https://www.dynamsoft.com/company/contact?utm_source=sampleReadme).
+If you have any questions, feel free to [contact Dynamsoft support](https://www.dynamsoft.com/company/contact?utm_source=sampleReadme).