Vscode-docs: Document how to work without tabs

[bpasero]

Usually I point users to this https://github.com/Microsoft/vscode/issues/6605 when they want to know how to work best without tabs in VS Code. I think since this question comes up more often we should add this to our Tabs docs page, maybe as full entry or just as FAQ.

Key points:

• the setting to disable tabs
• optional: disable the preview of editors
• optional: rebind keys to get as much back of the old experience as possible

/cc @egamma

[egamma]

In particular users are missing how to configure Ctrl+Tab to navigate in entire editor history.

[gregvanl]

Added https://vscode-eastus.azurewebsites.net/docs/editor/tabs#_working-without-tabs

[bpasero]

great!