Add dark mode (#199)

* Add passive dark mode to everything but codemirror

* Add dark theme support for Codemirror

* Make theme a user setting

* Fix button text size

* guard against undefined window

* Formatting and test fix

src/components/ActionButton.tsx

@@ -21,7 +21,7 @@ export const ActionButton = ({
   Element = 'button',
   children,
 }: ActionButtonProps) => {
-  const classNames = `group mono flex items-center gap-2 text-chalkboard-110 rounded-sm border border-chalkboard-40 hover:border-liquid-40 p-[3px] ${
+  const classNames = `group mono text-base flex items-center gap-2 rounded-sm border border-chalkboard-40 dark:border-chalkboard-60 hover:border-liquid-40 p-[3px] ${
     icon ? 'pr-2' : 'px-2'
   } ${className}`