Missing template lightbox-formatter.html.twig causes Twig\Error\LoaderError

Problem/Motivation

The lightbox_theme() hook in lightbox.module declares a theme hook named lightbox_formatter, which makes Drupal look for templates/lightbox-formatter.html.twig.

However, the template shipped with the module is named lightbox-image-formatter.html.twig (which corresponds to a lightbox_image_formatter theme hook). This mismatch causes a Twig loader error.

Steps to reproduce

1. Install and enable the Lightbox module
2. Configure an image field to use the Lightbox image formatter
3. View a content entity with that field

The following error is thrown:

Twig\Error\LoaderError: Template "modules/contrib/lightbox/templates/lightbox-formatter.html.twig" is not defined in "field.html.twig" at line 75. in Twig\Loader\ChainLoader->getCacheKey() (line 75 of themes/contrib/bootstrap5/templates/field/field.html.twig)

Proposed resolution

Rename the template lightbox-image-formatter.html.twig to lightbox-formatter.html.twig to match the existing theme hook.