chore: Separate extensions by app (#3905)

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

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

extensions/tumblr/stub/src/main/java/com/tumblr/rumblr/model/TimelineObject.java

@@ -0,0 +1,8 @@
+package com.tumblr.rumblr.model;
+
+public class TimelineObject<T extends Timelineable> {
+    public final T getData() {
+        throw new UnsupportedOperationException("Stub");
+    }
+
+}

extensions/tumblr/stub/src/main/java/com/tumblr/rumblr/model/TimelineObjectType.java

@@ -0,0 +1,4 @@
+package com.tumblr.rumblr.model;
+
+public enum TimelineObjectType {
+}

extensions/tumblr/stub/src/main/java/com/tumblr/rumblr/model/Timelineable.java

@@ -0,0 +1,5 @@
+package com.tumblr.rumblr.model;
+
+public interface Timelineable {
+    TimelineObjectType getTimelineObjectType();
+}