chore(code editor): add headerMainContent prop to example (#11720)

Author: Mash707

packages/react-code-editor/src/components/CodeEditor/examples/CodeEditorShortcutMainHeader.tsx

@@ -90,6 +90,7 @@ export const CodeEditorShortcutMainHeader: React.FunctionComponent = () => {
         value="Mac"
       />
       <CodeEditor
+        headerMainContent="Header main content"
         shortcutsPopoverProps={shortcutsPopoverProps}
         isLanguageLabelVisible
         code="Some example content"