Make preview mode a button, not just a gesture

[eugenesvk]

What

Make preview mode easier to enable

Why

Currently markdown preview mode is an undiscoverable gesture, for example, #305 (comment)

How

By adding a "Preview markdown" button

• In the options menu near Publish
• (configurable) as a separate top level button in the toolbar

[dangermattic]

Thanks for reporting! 👍