Update installation steps for Windows / Mac OS X for tfjs-node in REA…

[gaikwadrahul8]

I have updated Windows / Mac OS X Requires Python 2.7 section of tfjs-node for installing which seems outdated and as per the official documentation of node-gyp, " node-gyp requires that you have installed a supported version of Python. " I recommend updating the tfjs-node documentation aligning it with node-gyp requirements. Please do the needful or I welcome any suggestions or feedback to update outdated tfjs-node official documentation from your end. Thank you.

Addressing this issue will also resolve Github issue https://github.com/tensorflow/tfjs/issues/7716

[gbaned]

Hi @gaikwadrahul8 Your branch is out of date, can you please update your branch? Thank you!