Allow for component_prefix / component_suffix

Problem/Motivation

It would be nice if users could add arbitrary markup to the top and bottom of components in the Svelte app by injecting them. While this doesn't add full "themability" of the Svelte app, it does tackle a lot of potential use cases.

Proposed resolution

Allow an empty div or variable that can be dropped above cards or below cards, ex.g., or above/below the ProjectGrid, ex.g.

Ideally we could read from some Drupal twig files and use Drupal.theme on the frontend or something, or read out of drupalSettings.