Add ci pipeline to PR: Compile under esp-idf new build sytem

Created by: andreaskuster

I extended your PR bblanchon#1562 with the continuous integration pipeline functionality.

There are a few other PRs open to make this working (namely, the Ethernet library has to be ported as well):

Add esp-idf cmake build system component registration arduino-libraries/Ethernet#164 After this has been resolved, we can continue in the merge process of the actual PR to ArduinoJson