Add an end to end fixture that is a Single Page Application

What does this MR do?

Adds a single page application end to end test fixture. This will be used when Browserker is fully integrated.

What are the relevant issue numbers?

Relates to https://gitlab.com/gitlab-org/security-products/analyzers/browserker/-/issues/4.

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Job definition example
  • Vendored CI Templates (also in CE)
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer