replit/polygott ? reverse-engineered prompt

Build me a project that can create one Docker image with a bunch of programming languages installed and ready to use, kind of like a shared runtime image for an online coding environment.

I want it to read simple language config files, generate the build scripts from those configs, and let me build, run, and test either everything or just one language at a time. It should also be able to detect what language a project is using from the files in the folder, then pick the right entry point and run command.

Please include a clean way to add a new language, with support for install steps, packages, version checks, and simple test cases that verify the language works by running sample code and checking the output. If you need to look up current Docker or build docs online, go ahead.