Allow for configuration files in .devcontainer

Currently I don't seem to know a good way to have container-specific settings, tasks, and launch configurations. The closest thing to it is to set up settings.json, tasks.json, and launch.json in the workspace .vscode folder, but then it applies to the workspace when you open it normally. It would be ideal if we could have those same files in the .devcontainer folder and have vscode pick them up from there when the folder is opened in the container. Currently the closest thing to it is in .devcontainer/devcontainer.json, there is a settings key which is similar to having settings.json, but i don't see anything for tasks or launch.