AoFileUpload: UI Enhancements

AC

- Files can be picked by drag/drop onto the input, or by clicking a button
- There are unique modifier classes applied to the input when:
- The user is dragging a file, but not hovering over the input
- When the user is dragging a file AND hovering over the input
- When a file is picked, we see an image, the filename, and a remove button
- the remove button removes the item from the file list
- when all items are removed, the input returns to initial state
- if the filename is too long to be shown, it is truncated with "..."
- When multiple files are added, it will stretch the vertical size of the input to fit
- prop that will render the `multiple` attribute on the input ([W3S](https://www.w3schools.com/tags/att_input_multiple.asp))
- prop for passing thru accepted file types ([W3S](https://www.w3schools.com/jsref/prop_fileupload_accept.asp)
- Choose File button can be accessed by keyboard navigation
- Same as other input requirements:
- Label is required but can be hidden
- There is the same space for information text / invalid message