Improving examples | Cogs (Not extensions)

[bleudev]

Summary

Add example with cogs (not extensions) from this issue #2525 (fix #2525)

Checklist

• [ ] If code changes were made then they have been tested.
  • [ ] I have updated the documentation to reflect the changes.
• [x] This PR fixes an issue.
• [ ] This PR adds something new (e.g. new method or parameters).
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
• [ ] This PR is not a code change (e.g. documentation, README, ...)

[GoogolGenius]

Please run this through black.

[bleudev]

Please run this through black.

Ok

[bleudev]

@Rapptz pls review this pull