Make the installation scripts install Node and tns

Currently our recommended quick installation is a three-step process: install Node, install tns, and then run our setup scripts. Even though those steps are relatively minimal, a surprising number of people get tripped up going through them. See https://github.com/NativeScript/docs/pull/585 for an example.

I want to propose that we change the installation scripts to install everything—Node, tns, and the various system requirements. The scripts could detect whether Node is installed, as to avoid undoing a user’s installation unknowingly.

A single script would simplify the documentation considerably, but it would probably be a non-trivial engineering effort. And with installers in the works perhaps this isn’t worth the effort. But I wanted to open this up to see what people think.

Thoughts?

この issue ではファイル、テスト、エントリーポイントが指定されていないため、まずインストールスクリプトとクイックセットアップのドキュメントを見つけます。変更が完了すると、スクリプトが Node、tns、システム要件をインストールしつつ既存の Node のインストールを検出し、ドキュメントはより簡単なセットアップフローに縮小されます。