provide "Waterfall Flexible Toolbar" of material design spec

[nimo23]

This is a (multiple allowed):

• [x] enhancement

• Framework7 Version: 2

Please provide

• Waterfall Flexible Toolbar
• Waterfall Toolbar Fix Last Row
• Waterfall Flexible Toolbar with Custom Style

from the official "Material Design Spec":

• https://material-components-web.appspot.com/toolbar/index.html
• https://material.io/components/web/catalog/toolbar/

The different kinds of "Toolbars" can be enabled by adding css class within toolbar, for example:

• .toolbar-flexible
• .toolbar-fix-row
• .toolbar-flexible-style

[matthewbecker1990]

Ref: https://github.com/framework7io/framework7/issues/1806