Separate .nuxt folders for docker and local setup

Creating a separate volume for .nuxt/ where nuxt stores its transpiled
files ensures that both local and docker setup are isolated from each
other. E.g. on Linux I see these annoying owner permission errors,
because the user in the docker environment is called `root` not my user
on my host system `robert`.

This might be interesting for @mattwr18 too

docker-compose.override.yml

@@ -9,8 +9,10 @@ services:
       - .:/nitro-web
       - node_modules:/nitro-web/node_modules
       - node_modules_styleguide:/nitro-web/styleguide/node_modules
+      - nuxt:/nitro-web/.nuxt
     command: yarn run dev
 
 volumes:
   node_modules:
   node_modules_styleguide:
+  nuxt: