resolves #135

• Use new cacheDir option (replacing plugin)
• Set server.fsServer.root option to allow serving from rootDir rather than buildDir (.nuxt)

Current issues:

• The request url "/@id/defaultexport:<rootDir>/.nuxt/components/plugin.js" is outside of vite dev server root "<rootDir>"
  • [vite] @id to be handled or isolation checked after resolveId hook?
  • alternative: change defaultexport implementation?
  • alternative: start enforcing default export by nuxt plugins? (even if they don't need. this reduces module support but makes it easier for us)
• The request URL "<repoDir>/node_modules/ufo/dist/index.mjs" is outside of vite dev server root "<rootDir>". (repo is not a workspace but contains sub directory)
  • [vite] Support root as array? (to include nuxt.options.modulesDir[])
  • alternative: lookup for lockfile instead?

Update: fsServe isolation is disabled as a workaround