How to add new languages? What is the procedure?

I have left theia for a while now so i have forgotten this. What is the procedure to add a new language to my web running instance? I mean full language support including compile and stuff online.
Now for adding autocomplete I can use VS-Code extensions right? But how do I add compile and run support?
Thank you i want to know whatever is possible in this field

@Arijit265 thank you for the discussion, language-support including debugging, and other features are contributed by vscode plugins. You can either add them by default to your application by specifying them in your application’s package.json (example), or letting users install them at runtime through the extensions-view. You’ll need to ensure that the proper environment and tooling is present for them to work correctly, especially in a browser context. For example, we have docker images which setup the environment and include language support (example).

Thank you @vince-fugnitto i was really puzzled up with this stuff

Since this was asked by me so I should contribute to it too. I found a way around.
You can use code runner extension and set the enviroment variable PATH according to your requirements. It did work for me
Edit: The code runner is a vs code extension that can run i guess over 40 languages if provided with a path and compiler.