cli: remove support for .icon.svg imports

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

docs/getting-started/configure-app-with-plugins.md

@@ -82,11 +82,20 @@ import ExtensionIcon from '@material-ui/icons/Extension';
 
 You can also use your own SVGs directly as icon components. Just make sure they
 are sized according to the Material UI's
-[SvgIcon](https://material-ui.com/api/svg-icon/) default of 24x24px, and set the
-extension to `.icon.svg`. For example:
+[SvgIcon](https://material-ui.com/api/svg-icon/) default of 24x24px, and wrap
+the SVG elements in a `SvgIcon` component like this:
 
 ```tsx
-import InternalToolIcon from './internal-tool.icon.svg';
+import SvgIcon, { SvgIconProps } from '@material-ui/core/SvgIcon';
+
+export const ExampleIcon = (props: SvgIconProps) => (
+  <SvgIcon {...props}>
+    <g>
+      <path ... />
+      <path ... />
+    </g>
+  </SvgIcon>
+);
 ```
 
 On mobile devices the `Sidebar` is displayed at the bottom of the screen. For