Add a license to the repository

I recently came across your project Quantum-Computing and I noticed that the repository github.com/Ecaterina-Hrib/Quantum-Computing currently does not have a license specified.

Why Adding a License is Important?

As [GitHub documents](https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/licensing-a-repository)
>Public repositories on GitHub are often used to share open source software. For your repository to truly be open source, you'll need to license it so that others are free to use, change, and distribute the software.

Would be possible to add a valid license to this repository? Probably something really OpenSource such as the [Apache 2.0 license](https://www.apache.org/licenses/LICENSE-2.0) would fit really well.

Thanks!

Review the repository's current licensing status and GitHub's license guidance first. Add a valid open-source license, with Apache 2.0 suggested in the issue, and confirm that the repository has a specified license.

Written by the indexing model from the issue text.