chore: Inform users/visitors about move to GitLab

README.md

 ##### Fork of https://github.com/jdrouet/docker-with-buildx -> git.griefed.de -> github.com/Griefed
 
+# Sources, GitHub, GitLab and Mirroring and all that good stuff
+
+Repositories on GitHub are now for issues only. I've set up my own installation of GitLab and moved all my repositories over to [Git.Griefed.de](https://git.griefed.de/users/Griefed/projects). Make sure to check there first for the latest code before opening an issue on GitHub.
+
+For questions, you can always join my [Discord server](https://discord.griefed.de) and talk to me there.
+
+---
+
 # Docker image with buildx pre-installed
 
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