[docs]: Theme.AppCompat example link returns 404 (flutter-stripe#551)

Co-authored-by: jonasbark <[email protected]>

Author: maranix

README.md

@@ -45,7 +45,7 @@ dart pub add flutter_stripe
 
 - Android 5.0 (API level 21) and above
 - Kotlin version 1.5.0 and above: [example](https://github.com/flutter-stripe/flutter_stripe/blob/79b201a2e9b827196d6a97bb41e1d0e526632a5a/example/android/build.gradle#L2)
-- Using a descendant of `Theme.AppCompat` for your activity: [example](https://github.com/flutter-stripe/flutter_stripe/main/example/android/app/src/main/res/values/styles.xml#L15), [example night theme](https://github.com/flutter-stripe/flutter_stripe/blob/main/example/android/app/src/main/res/values-night/styles.xml#L16)
+- Using a descendant of `Theme.AppCompat` for your activity: [example](https://github.com/flutter-stripe/flutter_stripe/blob/main/example/android/app/src/main/res/values/styles.xml#L15), [example night theme](https://github.com/flutter-stripe/flutter_stripe/blob/main/example/android/app/src/main/res/values-night/styles.xml#L16)
 - Using an up-to-date Android gradle build tools version: [example](https://github.com/flutter-stripe/flutter_stripe/blob/main/example/android/build.gradle#L9) and an up-to-date gradle version accordingly: [example](https://github.com/flutter-stripe/flutter_stripe/blob/main/example/android/gradle/wrapper/gradle-wrapper.properties#L6) 
 - Using `FlutterFragmentActivity` instead of `FlutterActivity` in `MainActivity.kt`: [example](https://github.com/flutter-stripe/flutter_stripe/blob/79b201a2e9b827196d6a97bb41e1d0e526632a5a/example/android/app/src/main/kotlin/com/flutter/stripe/example/MainActivity.kt#L6)