It is recommended to set up an STLIB_PATH env variable pointint to the root directory where the ST-LIB is located so that other team tools work out of the box. Many tutorials exist on how to set an environment variable in different OSs, you should easily find one by googling it.
To use it you must install Dev Containers extension on VSCode and Docker. Be careful,use the instructions related to your OS, as docker doesn't work the same way in all OS's. Then, when you open this folder in VSCode, you will have the ability to reopen it inside the container. Don't worry, the first time you do it will take some time.