Add YouTrack logo

Purpose

As per Add integration logo: YouTrack (gitlab#367584 - closed), we're adding YouTrack logo to our library. IntegrationYouTrack

Following the spreadsheets.

As noted on the Third-party Trademark Tracker, JetBrains has approved use of their YouTrack logo on the integrations page.

Screenshots

Checklist

For a new icon and/or illustration:

• Link to related design issue:
• 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.