doc: add supported platforms list
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
documentation is changed or added -
commit message follows commit guidelines
Affected core subsystem(s)
doc
Talked to Rod, going to take over landing the supported platform list from him. Earlier review/discussion was in: https://github.com/nodejs/node/pull/8922/commits/d883278e9647f6abc35a66e582954d8e318d6955