message: Add mobile device field to the issue template.
diff: @@ -15,6 +15,7 @@ If you open a GitHub issue, here is our policy:
  ### System information
  - **Have I written custom code (as opposed to using a stock example script provided in TensorFlow)**:
  - **OS Platform and Distribution (e.g., Linux Ubuntu 16.04)**:
  +- **Mobile device (e.g. iPhone 8, Pixel 2, Samsung Galaxy) if the issue happens on mobile device**:
  - **TensorFlow installed from (source or binary)**:
  - **TensorFlow version (use command below)**:
  - **Python version**:
  