Dockerfile not building with `ARG UBUNTU_RELEASE="latest"`

[Jojeker]

Hello!

We were trying to build the docker container and noticed that the current file does not build, because the latest Ubuntu release does not have nuget in its repositories. We notice that this is related to the UBUNTU_RELEASE variable set to latest 1. We suggest Using the 22.04 LTS, which builds successfully.

Thanks for the project; it is really cool!

Best,
DieBüntzlis

[trufae]

Please send a pr with the fix