Update README.md.

Author: Isira-Seneviratne

README.md

@@ -13,6 +13,8 @@ If you're using Gradle, you could add NewPipe Extractor as a dependency with the
 1. Add `maven { url 'https://jitpack.io' }` to the `repositories` in your `build.gradle`.
 2. Add `implementation 'com.github.TeamNewPipe:NewPipeExtractor:v0.20.1'`the `dependencies` in your `build.gradle`. Replace `v0.20.1` with the latest release.
 
+**Note:** To use NewPipe Extractor in projects with a `minSdkVersion` below 26, [API desugaring](https://developer.android.com/studio/write/java8-support#library-desugaring) is required.
+
 ### Testing changes
 
 To test changes quickly you can build the library locally. A good approach would be to add something like the following to your `settings.gradle`: