Doc Alignment: CommandBarFlyout Updates

[stmoy]

Describe the bug

Several updates requested:

• Make the flyout appear over the image instead of off to the side
• Add splitbutton with flyout to sample
• Add icons to secondary menu
• Add code from doc to create custom zoom flyout
• Add RichEditBox as a new sample on the page to show default text CommandBarFlyout

https://docs.microsoft.com/en-us/windows/uwp/design/controls-and-patterns/command-bar-flyout

[Poopooracoocoo]

Add icons to secondary menu

Is there no select all icon in the MDL2 assets? The Office apps have an icon for select all

[marcelwgn]

There is this icon, but I am not sure if people actually associate it with select all:

[Jay-o-Way]

Is this still an issue with the latest version?