Allow VSCode-wide security configuration.

TL;DR: Allow users to disallow .devcontainer files from taking certain actions.

Currently, using Dev Containers in any repository where you don't monitor the full changelog is dangerous. This comes from the fact that a malicious .devcontainer file can result in total system compromise. It can do this in a few ways ranging from mounting the entire host filesystem inside the container, having a malicious initializeCommand, or running a container with --privileged.

Dev containers, if properly protected, can give users a very significant security sandbox to work in, allowing them to work with third party codebases without having to worry so much about their whole system being compromised if someone slipped in something sneaky.

Small Request:
Add configuration options (settings.json) that allow the user to disable certain features. While a full security audit would be valuable, at the very least it should allow disabling the usage of --privileged, disallowing mounting of any volumes outside the current directory, and disabling the initializeCommand script entirely.

Bigger Request:
Even better would be if it could be made so that the there is an option to enable, disable, or prompt when these features are utilized. This way, a user could still leverage those features for repositories they personally maintain, but could avoid having them covertly used by malicious repositories.

At the moment, users wanting to use dev containers essentially need to load the folder in VSCode untrusted mode, fully audit .devcontainer, and then open it in a remote container in trusted mode. A middle ground would go a long way to making things far safer, with what seems like a fairly minor change to the extension.