The custom theme document talks about System Icons, then immediatly ignores the existance of these in the `Sidebar Sub-menu` example a couple of paragraphs later.
This commit updates the docs to make use of these icons, as well as adding an icon for resource types to the default icons.
Also updated the sidebar in example app to use this same approach
Signed-off-by: Alex Crome <afscrome@users.noreply.github.com>
Alex Crome
575d9178ef