fix codemirror stylesheets

- Closes #775

components/Meta.js

@@ -8,7 +8,7 @@ import Typography from './style/Typography'
 const HIGHLIGHTS_ONLY = ['shades-of-purple', 'vscode']
 const LOCAL_STYLESHEETS = ['one-light', 'one-dark', 'verminal', 'night-owl', 'nord']
 const CDN_STYLESHEETS = THEMES.filter(
-  t => LOCAL_STYLESHEETS.indexOf(t.id) < 0 && HIGHLIGHTS_ONLY.indexOf(t.id) < -1
+  t => LOCAL_STYLESHEETS.indexOf(t.id) < 0 && HIGHLIGHTS_ONLY.indexOf(t.id) < 0
 )
 
 export function Link({ href }) {