Reject signature request if user goes back from page (#54)

components/SignRequest.tsx

@@ -1,12 +1,13 @@
 import React, { useEffect, useMemo, useState } from 'react';
 import { Alert, Image, ScrollView, View } from 'react-native';
-import { ActivityIndicator, Button, Text } from 'react-native-paper';
+import { ActivityIndicator, Button, Text, Appbar } from 'react-native-paper';
 
 import { useNavigation } from '@react-navigation/native';
 import {
   NativeStackNavigationProp,
   NativeStackScreenProps,
 } from '@react-navigation/native-stack';
+import { getHeaderTitle } from '@react-navigation/elements';
 
 import { Account, StackParamsList } from '../types';
 import AccountDetails from './AccountDetails';
@@ -160,6 +161,27 @@ const SignRequest = ({ route }: SignRequestProps) => {
     navigation.navigate('Laconic');
   };
 
+  navigation.setOptions({
+    // eslint-disable-next-line react/no-unstable-nested-components
+    header: ({ options, back }) => {
+      const title = getHeaderTitle(options, route.name);
+
+      return (
+        <Appbar.Header>
+          {back && (
+            <Appbar.BackAction
+              onPress={async () => {
+                await rejectRequestHandler();
+                navigation.navigate('Laconic');
+              }}
+            />
+          )}
+          <Appbar.Content title={title} />
+        </Appbar.Header>
+      );
+    },
+  });
+
   return (
     <>
       {isLoading ? (