Update all contributor

What does this MR do?

I inserted myself as a contributor.

Questions

• Is there a guideline when this is common?
• After how long do we want to remove people who have become inactive?
• Are there any other active ones that should add or update about this MR / branch?

Screenshots (if applicable)

Any relevant screenshots if this is a design / frontend change

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• joined #foodsharing-beta channel at https://slackin.yunity.org
• added an entry to CHANGELOG.md (description, merge request link, username(s))
• Once your MR has been merged, you are responsible to update the #foodsharing-beta Slack channel about what has been changed here. They will test your work in different browsers, roles or other settings