Mail: Floating action button

[kulmann]

Initial Checklist

• I understand this is a user story and questions should be posted in the Community Discussions
• I searched issues and couldn’t find anything (or linked relevant results below)

User Story

• As a user I want to have an as easy as possible way of writing a new email so that I don't need to search the UI.

User Value

Ease of use

Acceptance Criteria

• Floating action button is a new component in the design system
• Floating action button may take multiple handlers/routes and displays them as stacked buttons OR FAB only takes one handler/action and directly navigates on click event
• Floating action button will only be visible in mobile view
• Floating action button will only be visible in the mail list view - We might think about also displaying it in the Mailbox Tree view later
• The write new email button for desktop must be moved to Mailbox view

Screenshots