MenuBar: optional dropdown indicators on menu bar buttons

[rolfsmeds]

trafficstars

Description

Optional drop-down indicators on menubar buttons with dropdowns

Acceptance criteria

• [ ] Theme variant (e.g. dropdown-indicators/ MenuBarVariant.DROPDOWN_INDICATORS)
• [ ] Renders dropdown indicators on menubar buttons that have dropdown menus
• [ ] Does not render the indicator on the overflow menu button
• [ ] Looks good combined with small and tertiary variants

Feature request ticket: https://github.com/vaadin/web-components/issues/7345

Implementation proposal: https://github.com/vaadin/web-components/issues/7345#issuecomment-2095354928

Visual design

General criteria

• [ ] APIs reviewed

• [x] Design

• [ ] Performance

• [ ] UX/DX tests in Alpha

• [ ] Documentation: (to be added as a new subsection to the Styles section (below Default variants)

• [ ] How to test?

• [ ] Limitations:

Security

• [x] Security implications have been taken into account (elaborate or link to product security requirement specification if there are implications)