Make Monaco overflow fixed

fixes codesandbox#554

Author: Ives van Hoorne

packages/app/src/app/components/CodeEditor/Monaco/index.js

@@ -987,6 +987,7 @@ class MonacoEditor extends React.Component<Props, State> implements Editor {
       lineHeight: (settings.lineHeight || 1.5) * settings.fontSize,
       folding: true,
       glyphMargin: false,
+      fixedOverflowWidgets: true,
     };
   };
 

packages/app/src/app/pages/Sandbox/Editor/Header/elements.js

@@ -8,7 +8,6 @@ export const Container = styled.div`
   background-color: ${props => props.theme.background2};
   font-size: 1.2rem;
   color: rgba(255, 255, 255, 0.7);
-  z-index: 40;
   margin: 0;
   height: 3rem;
   font-weight: 400;