Add linux logo

Purpose

Add linux logo svg.

See https://gitlab.com/gitlab-com/legal-and-compliance/-/issues/1340

Screenshots

Checklist

For a new icon and/or illustration:

• Link to related design issue: gitlab#383139[Runner-registration-page.png]
• Link to related task: gitlab#390423 (comment 1378392586)
• [-] If this adds an icon ensure that it follows the new icon checklists.
• If this adds an illustration ensure that it follows the new illustration checklists.

For third-party trademarks:

• If this adds or updates an icon or illustration that includes a third-party trademark, ensure that it follows the process for adding third-party trademarks to GitLab.