contrib: Write up how to test Tasks builds on iPhone & iPad

contributing/Testing/How do I test a GitHub build of the Tasks plugin.md

@@ -35,3 +35,18 @@ You can use these steps to install the built plugin either in to the Tasks-Demo
 3. Expand the downloaded zip file
 4. Copy the files in the expanded folder to the `.obsidian/plugins/obsidian-tasks-plugin/` folder in your vault, over-writing the previous files.
 5. Restart Obsidian.
+
+## Option 3: On iPhone and iPad, in local storage
+
+1. Download the build's Zip file - see above.
+2. Uncompress the Zip file
+3. Move the expanded folder to location `On My iPhone/Obsidian/`, or the iPad equivalent.
+    1. Press-and-hold on the uncompressed folder
+    2. Select Move
+    3. Then navigate to local storage, and the Obsidian folder inside
+4. Restart Obsidian
+5. Open the folder as a vault
+
+## Option 4: With Obsidian Sync
+
+It is also possible to add the test vault to [Obsidian Sync](https://help.obsidian.md/Obsidian+Sync/Introduction+to+Obsidian+Sync), if you subscribe to that facility.