Track Share Icons Click

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

There is no way to track a click of a share option in the Share Menu that appears on click of the Share Button (top right of the story UI).

We want to know, beyond a click of the Share Button, that the user has clicked a share option and what option they clicked.

## Describe alternatives you've considered

There is no existing way to track the user's choice in the Share Menu. We realize that the native UI (seen on mobile browsers) cannot be tracked, however we still want to track interaction inside the Share Menu when it's part of AMP.

## Additional context

We're using version 2103020156003.

The issue does not name files or tests. Start by locating the AMP Share Menu and the existing Share Button tracking, then determine how menu choices are represented separately from native mobile UI. Done means AMP-rendered share-option clicks expose which option was selected while native UI remains unsupported.

Written by the indexing model from the issue text.