chore: Separate extensions by app (#3905)

extensions/reddit/stub/src/main/AndroidManifest.xml

@@ -0,0 +1 @@
+<manifest/>

extensions/reddit/stub/src/main/java/com/reddit/domain/model/ILink.java

@@ -0,0 +1,7 @@
+package com.reddit.domain.model;
+
+public class ILink {
+    public boolean getPromoted() {
+        throw new UnsupportedOperationException("Stub");
+    }
+}