Add new product icon > comment-lines

Purpose

Add comment-lines icon.

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.

Relastes to #351 (closed)