warn of data loss on reloading registration page

Author: yaya-usman

src/components/views/auth/AuthBody.tsx

@@ -17,6 +17,16 @@ limitations under the License.
 import React from 'react';
 
 export default class AuthBody extends React.PureComponent {
+    componentDidMount() {
+        const unloadCallback = (event) => {
+            event.preventDefault();
+            event.returnValue = "";
+            return "";
+        };
+        window.addEventListener("beforeunload", unloadCallback);
+        return () => window.removeEventListener("beforeunload", unloadCallback);
+    }
+
     public render(): React.ReactNode {
         return <div className="mx_AuthBody">
             { this.props.children }