Use Web IDE to create new files in empty repos

What does this MR do?

Issue: #27535 (closed)

In a blank repository, the buttons for new files should be linked to the Web IDE.

In this MR, the following buttons have been linked to the Web IDE in a new repo:

• New File
• Add CHANGELOG
• Add README
• Add CONTRIBUTING
• Add LICENSE

However, it was decided in #247483 (comment 411348424) that the "Add CI/CD" buttons would be linked to the single file editor at all times (for both new and old repos).

Screenshots

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

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team