Test vulnerability details entry file

What does this MR do?

It adds integration tests for the init-script that is responsible for rendering the vulnerability details page.

Aside from adding the specs it also adds the jest-dom library as a dependency and adds it to the frontend integration-specs setup.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Related to #220290 (closed)