Make fork project form responsive

MR	Changes
!53544 (merged)	Implement fork project form
tbd	Implement fork info in vue (and add fork project icon)
tbd	Add validation to form
tbd	Add project-slug auto kebab case of project-name
👉 this MR	make form responsive
tbd	Docs

This feature is behind a Feature Flag, to turn on:

Feature.enable(:fork_project_form)

What does this MR do?

This MR just ensure the fork form is responsive

Small	Medium	Large

Screenshots (strongly suggested)

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

Related to #15013 (closed)