Feature Request: --paper-input-container for paper-dropdown-menu-light

[naoak]

Description

paper-dropdown-menu has a feature to customize styles (e.g. paddings) of the dropdown trigger via --paper-input-container, but paper-dropdown-menu-light does not.

The styles of dropdown trigger are fixed at here. I think it would be nice if it had a custom style variable as paper-dropdown-menu has.

[evtaranov]

It will be awesome if you add such custom mixin here