[amp story shopping] Add Object typedef for shopping data

[processprocess]

Description

A typedef for SHOPPING_DATA will help developers/reviewers understand the code.

Check out the example for interactives in component in store service here and here.

This is a follow up to this comment.

[jshamble]

Closing this as I am solving it in #36699

[processprocess]

Re opening this.
Please do not close issues before they are merged.
Please add "Closes #36911" to the description of #36757 that way it will automatically be closed when that PR is merged.