Devcontainer support for SD build

[pbk20191]

It would be really nice to have docker container environment for SD build flow. Since it will be more lighter than pure virtual machine and get benefit from prebuilt image.

This configuration expects the Xilinx tools all installed in default location tools/Xilinx in host. But users can change path if they want to.

[skalade]

Would you be willing to turn this into a regular dockerfile, without .devcontainer? We would be more interested in that use-case. This would be a nice alternative to vagrant.