todosapp: polish for demo
todosapp: polish for demo

- trim whitespace in "join list" input to ensure it's valid
  (bindu had leading whitespace, causing failed join RPC,
  during testing this morning)
- focus "share" input box when sharing pane opens

Change-Id: If59faffb28ba0659021435292de9617663b5cef7

vanadium/todos