Propose deletion of .devcontainer as it is out of date #390

It looks like our devcontainer config is out of date (some python packages dont exist anymore on the container ubuntu distro) but it also is kinda awkward to use usb devices through WSL for flashing, so I am wondering if anyone is really using the devcontainer for MF firmware development?

IF not, I think the config is just confusing since new contributors might mistakenly think it is the preferred workflow since it exists.

@neilenns it looks like this is 5 years old file, and platformio seems to do the job well, so should we just axe this?