Dashboard: should scroll to bottom of input after adding item

[JessicaYeh]

When the input box grows large enough that the scroll bar appears, and more items are added, the scroll position doesn't automatically go to the bottom. Typing item names mostly doesn't have this issue, since typing a character will cause the input to jump to the cursor location (except that pressing Enter to select an item does not jump to the bottom). This issue is easiest to reproduce when you only use the drop down menu instead of typing to choose items.