MAINTAINERS: add @sebastiaanspeck as org member

[kbdharun]

Hi, @sebastiaanspeck! After joining as a collaborator in the repository, you have been regularly performing maintenance tasks.
Thank you for that!
According to our community roles documentation, you've now met the thresholds to be effectively considered an active maintainer of the project.
To publicly acknowledge that fact, we'd like to add you to the tldr-pages organization.

If you accept the invitation, we ask you to make your membership public, and (in case you don't already) start hanging out in our Matrix chat room.
Additionally, consider subscribing to the notifications from the various repositories under the tldr-pages organization.
As one of the public faces of the tldr-pages project, it's also especially important that you follow and encourage the project
governance principles.

How does that sound? Are you up for it?

[sebastiaanspeck]

Hi, @kbdharun! Thank you for inviting me as org member. I would sure love to become an organization member of the tldr-pages organization.

[kbdharun]

Congratulations, I have sent an invite. Feel free to close this issue with a PR. (Once accepted, set your membership as public in https://github.com/orgs/tldr-pages/people)