add Nuxt DevTools?

[userquin]

• prepare integration
• list Vuetify components: there is no need since we now load the components via Nuxt
• allow change colors
• allow switch theme and list themes
• allow switch locale and list locales

[AndreyYolkin]

Scoped to 2.0.0. The original "list Vuetify components" item is already covered by the generic Nuxt DevTools (components are loaded via Nuxt), so the remaining scope here is a module-specific DevTools tab: switch/list themes, change colors, and switch/list locales.