Add info to build.gradle and settings.gradle on how to use a local

NewPipe extractor version.

settings.gradle

@@ -1 +1,11 @@
-include ':app'
+include ':app'
+
+// Use a local copy of NewPipe Extractor by uncommenting the lines below.
+// We assume, that NewPipe and NewPipe Extractor have the same parent directory.
+// If this is not the case, please change the path in includeBuild().
+
+//includeBuild('../NewPipeExtractor') {
+//    dependencySubstitution {
+//        substitute module('com.github.TeamNewPipe:NewPipeExtractor') with project(':extractor')
+//    }
+//}