Make code consistent with the comment above

webpack.config.js

@@ -26,7 +26,7 @@ const cssThemes = {
 
 function getActiveThemes() {
     // We want to use `light` theme by default if it's not defined.
-    const theme = process.env.MATRIX_THEMES ?? 'dark';
+    const theme = process.env.MATRIX_THEMES ?? 'light';
     const themes = theme.split(',').filter(x => x).map(x => x.trim()).filter(x => x);
     return themes;
 }