Externalize i18n strings from viewer_swicher.html.haml

What does this MR do?

To support multilingualization.

Screenshots

Recreation

Vue is used for the viewer switcher in the project repo. I think this one is only used when browsing archives.

I spun up a quick project with a README.md and the following .gitlab-ci.yml:

some-job:
    script:
        - echo "hello"
    artifacts:
        paths:
            - "README.md"

Ran a local runner then explored the artifacts using the browse button in the right sidebar from the job log/detail.

Then hovered and checked the switcher buttons in source 👌

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