I’d be happy to assist implementing language support for https://nim-lang.org/
It looks like they ship docker images already so there is nothing stopping you from using that as a part of your build.
What else did you have in mind for “support” for this language?
When adding a new project in the 2.0 UI the user is presented with a set of radio buttons to pick the language which trigger the display of an example yml file.
An example file for Nim could be provided - e.g. this chunk-> https://github.com/nim-lang/Nim/wiki/BuildServices#building-nim-projects-on-circle-ci-v20-with-docker