chore(ci): remove Shopify/shopify-cla-action (#2489)

- add CONTRIBUTING.md indicating DCO requirements for commits
- update LICENSE.md

Signed-off-by: Dominic Evans <dominic.evans@uk.ibm.com>

CONTRIBUTING.md

@@ -0,0 +1,46 @@
+## Contributing
+
+[fork]: https://github.com/IBM/sarama/fork
+[pr]: https://github.com/IBM/sarama/compare
+[released]: https://help.github.com/articles/github-terms-of-service/#6-contributions-under-repository-license
+
+Hi there! We are thrilled that you would like to contribute to Sarama.
+Your help is essential for keeping it great.
+
+Contributions to this project are [released][released] to the public under the project's [opensource license](LICENSE.md).
+By contributing to this project you agree to the [Developer Certificate of Origin](https://developercertificate.org/) (DCO).
+The DCO was created by the Linux Kernel community and is a simple statement that you, as a contributor, wrote or otherwise have the legal right to contribute those changes.
+
+Contributors must _sign-off_ that they adhere to these requirements by adding a `Signed-off-by` line to all commit messages with an email address that matches the commit author:
+
+```
+feat: this is my commit message
+
+Signed-off-by: Random J Developer <random@developer.example.org>
+```
+
+Git even has a `-s` command line option to append this automatically to your commit message:
+
+```
+$ git commit -s -m 'This is my commit message'
+```
+
+## Submitting a pull request
+
+0. [Fork][fork] and clone the repository
+1. Create a new branch: `git checkout -b my-branch-name`
+2. Make your change, push to your fork and [submit a pull request][pr]
+3. Wait for your pull request to be reviewed and merged.
+
+Here are a few things you can do that will increase the likelihood of your pull request being accepted:
+
+- Keep your change as focused as possible. If there are multiple changes you would like to make that are not dependent upon each other, consider submitting them as separate pull requests.
+- Write a [good commit message](http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html).
+
+## Further Reading
+
+- [Developer Certificate of Origin versus Contributor License Agreements](https://julien.ponge.org/blog/developer-certificate-of-origin-versus-contributor-license-agreements/)
+- [The most powerful contributor agreement](https://lwn.net/Articles/592503/)
+- [How to Contribute to Open Source](https://opensource.guide/how-to-contribute/)
+- [Using Pull Requests](https://help.github.com/articles/about-pull-requests/)
+- [GitHub Help](https://help.github.com)

LICENSE → LICENSE.md

@@ -1,4 +1,7 @@
+# MIT License
+
 Copyright (c) 2013 Shopify
+Copyright (c) 2023 IBM Corporation
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the