Updating Vuetify decorator example

The Vuetify decorator example was expecting that the labels from the theme switcher would exactly match the vuetify theme keys from the vuetifyOptions.  This change makes that association more explicit while also allowing the display labels to be different from the Vuetify theme keys.

code/addons/themes/docs/api.md

@@ -166,7 +166,7 @@ export const withVuetifyTheme = ({ themes, defaultTheme }) => {
       setup() {
         const theme = useTheme();
 
-        theme.global.name.value = selected;
+        theme.global.name.value = themes[selected];
 
         return {
           theme,
@@ -195,12 +195,13 @@ setup((app) => {
 
 export const decorators = [
   withVuetifyTheme({
+    // These keys are the labels that will be displayed in the toolbar theme switcher  
+    // The values must match the theme keys from your VuetifyOptions
     themes: {
       light: 'light',
       dark: 'dark',
-      customTheme: 'myCustomTheme',
+      'high contrast': 'highContrast', 
     },
-    defaultTheme: 'customTheme', // The key of your default theme
+    defaultTheme: 'light', // The key of your default theme
   }),
-];
-```
+];```