Add nRF Connect for VS Code to nRF91 quickstart

[beriberikix]

Details: https://www.loom.com/share/a4f1774efb6f464abd2e504532ca1540

[rajeev1986]

@beriberikix, this is a good step forward.
I initially covered the preview version of nRF Connect VScode through a walkthrough tutorial here and managed to get the Conexio Stratus board that is based on nRF9160 to compile, flash and even debug.

Thought to share with you!. Cheers

[beriberikix]

Really nice guide, thanks for sharing! Good resource for the community 💪