DIGITAL-486: Apply digital_gov theme styles to ckeditor preview

[rayestrada]

Jira ticket

https://cm-jira.usa.gov/browse/DIGITAL-486

Purpose

Apply basic digital_gov theme styles to ckeditor preview.

Note: that I applied this in a absolute minimum way to not affect the current theme styles or deployment workflow. Additionally since some element styles requires the 'usa-prose' wrapper this will not be compatible with ckeditor.

Deployment and testing

Local Setup

lando fe
lando drush cr

QA/Testing instructions

1. Log in to your local site and visit https://digitalgov.lndo.site/node/13/edit make sure you have your inspector set to disable cache.
2. Confirm that you are seeing shortcode styling applied in the wysiwyg.

Note: I think there are improvements that could make this better but would most likely require modifying styles in the theme which we want to avoid until after launch.

Checklist for the Developer

• A link to the JIRA ticket has been included above.
• No merge conflicts exist with the target branch.
• Automated tests have passed on this PR.
• A reviewer has been designated.
• Deployment and testing steps have been documented above, if applicable.

Checklist for the Peer Reviewers

• The file changes are relevant to the task objective.
• Code is readable and includes appropriate commenting.
• Code standards and best practices are followed.
• QA/Test steps were successfully completed, if applicable.
• Applicable logs are free of errors.