api21_icon.md in headdesk-0.9.0

- old
+ new
@@ -1,14 +1,27 @@
 # teak/api21_icon
 Ensures that the APK contains a notification icon for both Android 5+ (API 21+) as well as pre-Android 5, and that these are different icons.
 
+Also verifies following files have the specified image dimensions:
+* drawable-mdpi/[icon_v21].png     24x24
+* drawable-hdpi/[icon_v21].png     36x36
+* drawable-xhdpi/[icon_v21].png    48x48
+* drawable-xxhdpi/[icon_v21].png   72x72
+* drawable-xxxhdpi/[icon_v21].png  96x96
+
 ## Will Skip If
 * The Teak SDK is not present.
 
 ## Will Fail If
 * There is no drawable resource for `io_teak_small_notification_icon`.
 * There is no v21 drawable resource for `io_teak_small_notification_icon`
 * The drawable resources point to the same image.
+* The v21 drawable resources do not exist, or are the incorrect size
+    * `drawable-mdpi/[icon_v21].png` does not exist, or is not 24x24
+    * `drawable-hdpi/[icon_v21].png` does not exist, or is not 36x36
+    * `drawable-xhdpi/[icon_v21].png` does not exist, or is not 48x48
+    * `drawable-xxhdpi/[icon_v21].png` does not exist, or is not 72x72
+    * `drawable-xxxhdpi/[icon_v21].png` does not exist, or is not 96x96
 
 ## Exports
 The values for `io_teak_small_notification_icon` for less than v21, and v21+.
 
 ### Example