Add the `milvus` gem

[andreibondarev]

I want to contribute to this list and help the maintainers, so:

• [x] I've accepted the terms of the CC0 License;
• [x] I've added the topic rubyml to the contributed repository if appropriate.

[andreibondarev]

@arbox Another one :)

[arbox]

@andreibondarev , thank you for your contribution.

I'd encourage you to add to your relevant projects the following GitHub topics:

• https://github.com/topics/rubyml
• https://github.com/topics/ml
• https://github.com/topics/machine-learning

It would greatly enhance discoverability of your projects on GitHub.