Updating Dockerfile

Description

I would like to have Docker images being built again for this project and since the docker section looked a bit abandoned I decided to give it a cleanup, feedback and discussion is more than welcome!

Changes Proposed

As agreed with Kwoth on Discord I removed libopus, libsodium and python. All tests have passed and the CI/CD is not stuck anymore. I also took the opportunity to divide the Dockerfile in two different stages.

Details

This Dockerfile is now divided into two stages: the build stage and the runtime stage. The build stage uses the .NET SDK to build the application, and the runtime stage uses the .NET runtime to run the application. This multi-stage build process reduces the size of the final image by excluding the SDK and other build tools.

Notes

I am extremely new to GitLab's interface and this is my first MR for this project, if you have any questions, tip or doubts please feel free to ping me on Discord or here about it!