Add Blob Page to the repository vue app [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

This MR adds a blob page to the repository Vue app in preparation for Extending the repository Vue app to also show Blob's through Vue.

MR	status
Add Blob Page to the repository vue app	This MR
Add Blob content viewer to the repository app	✅ merged
Use Monaco in readonly mode to view blobs	🚧 in dev
Render blob viewer Vue app	🚧 Not started

Note: This MR is part of a bigger effort to refactor the refactor the repository browser to one Vue application, see &5531 (closed) for more details.

Changes in this MR are behind the :refactor_blob_viewer feature flag.

Screenshots

No UI changes are expected.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because the feature is behind a feature flag.
• Code review guidelines
• Merge request performance guidelines
• Style guides

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

Related to #323200 (closed)