Allow autocomplete to have a custom click handler on tap

## Describe the new feature or change to an existing feature you'd like to see

Hello,
I have a use case that I haven't found anything that mentions it in the docs. I want to be able to run a custom click handler for each auto-complete item. This will enable me to achieve this use case.

## Describe alternatives you've considered

I tried to use a single amp-script that does everything using javascript without any other amp components. It fell short and I had to redo everything using amp components, like auto complete, form, bind, etc.

## Additional context

The feature I'm trying to implement is an amp autocomplete that lets you search for areas, once you click an item, a custom handler should intercept that, does some transformations and saves generated url to local storage, after that the form is submitted to the backend where the user is redirected to that specific search area they clicked on.

When this user comes back in the future, they'll find a list of their previous searches below the amp autocomplete using an amp-list component.

Hope my use case is clear enough.

Start by locating the AMP autocomplete component and reviewing its existing item-selection and tap behavior, along with the related amp-form, bind, and amp-list documentation mentioned in the issue. Done should mean each autocomplete item can invoke a custom handler on tap while supporting the described transformation and form-submission flow.

Written by the indexing model from the issue text.