Web editor guide (#830)

* update quickstart web editor content

* update introduction

* update Editor modes section

* move component menu to Making changes section

* update page structure

* remove info about CLI

* update introduction

* update editor modes

* update git fundamentals

* add info on deployment branches

* update branch procedures

* update making changes section

* add file menu images

* update PR section

* update troubleshooting

* add PR tip

* add reviewer feedback

Author: ethanpalm