Add documentation about the code changes how to make vscode compile and run on ppc64le

[aryoda]

Great work this port (esp. since MS does not want to do this :-)

Feature request:

Please add a short documentation (eg. to the readme) to explain the major problems and applied changes to the original source code to make vscode ready-to-compile and working for ppc64le.

This could be "reverse-engineered" from the commits of course but I am asking for this to find a way to upgrade to the most-recent version and perhaps someone wants to maintain regular automated updates in future...