.devcontainer/devcontainer.json: Add devcontainer file

.devcontainer/devcontainer.json: Add devcontainer file

Tianocore maintains container images in the tianocore/containers repo
and stores container images within the GitHub container registry.

https://github.com/tianocore/containers

This change adds a devcontainer.json file to the edk2 repo. This
file's metadata and settings to configurate a development container
for a given well-defined tool and runtime stack.

More information about the devcontainer.json file is available here:
https://containers.dev/implementors/json_reference/

This file is recognized by popular tools such as GitHub Codespaces
and VS Code. In VS Code in particular, it makes it much easier for
a user to be aware a dev container exists (via UI notifications)
and to load the container.

A minimal number of VS Code extensions are specified that are useful
for edk2 development or to assist in complying with CI checks in
place in edk2.

Cc: Andrew Fish <afish@apple.com>
Cc: Chris Fernald <chris.fernald@outlook.com>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Oliver Steffen <osteffen@redhat.com>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>