Add mechanism to limit allowable view modes

Problem/Motivation

Generally speaking, some view modes are usually not a good candidate for inclusion in the list for content editors to choose from. It would be nice to have a way to limit the view modes to a limited subset that are known to work well with embedding.

I would be more than willing to build this feature and relevant tests if the maintainer would be open to merging it in.

Thank you!

Proposed resolution / Remaining tasks

• Add a settings form to the module that allows a user to limit which may be embedded.
• Add configuration schema definitions for the new configuration.
• Do an array intersect within \Drupal\entity_browser_block\Plugin\Block\EntityBrowserBlock::processTable that removes illegal choices from the #options array.
• Make the view mode field required in the table.
• Add a new permission for administering entity browser block configuration.
• Add a route to access the config form.
• Write some tests!
• User acceptance testing.

or

Would it make more sense to limit things on a per-entity-browser basis instead?

User interface changes

A new settings form for the module.

API changes

None

Data model changes

None