Add integrations logos

Purpose

We are adding integrations logos, as per &8370 (comment 1570755864), followed the spreadsheets.

It refers to:

• Add integration logo: Asana (gitlab#367579)
• Add integration logo: Telegram (gitlab#424477 - closed)
• Add integration logo: Atlassian Bamboo (gitlab#367609 - closed)
• Add integration logo: Buildkite (gitlab#367608 - closed)
• Add integration logo: Datadog (gitlab#367605)
• Add integration logo: Discord Notifications (gitlab#367604)
• Add integration logo: Jenkins (gitlab#367597)
• Add integration logo: Pushover (gitlab#367589 - closed)
• Add integration logo: PivotalTracker (gitlab#367591 - closed)

Screenshots

N/A

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.