Refine API doc for Picker
Refine API doc for Picker

- Use a typed function instead of `Function`
- Align listener parameter type with selection property (use `any`)

Change-Id: I30b81487ef8cfa0386d7306ee52b50b68eed3bee

eclipsesource/tabris-js,eclipsesource/tabris-js,eclipsesource/tabris-js