Add Salesforce logo

Purpose

Add Salesforce logo to support https://gitlab.com/gitlab-com/legal-and-compliance/-/issues/596. The file is PNG and is an official Salesforce logo from https://brand.salesforce.com/content/logo-guidelines.

Checklist

For a new icon and/or illustration:

• Link to related design legal 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.