chore(i18n): refactor and cleanup (#805)

* checkpoint

* finish

* docs

quartz/components/pages/404.tsx

@@ -1,11 +1,11 @@
-import { i18n } from "../../i18n/i18next"
+import { i18n } from "../../i18n"
 import { QuartzComponentConstructor, QuartzComponentProps } from "../types"
 
 function NotFound({ cfg }: QuartzComponentProps) {
   return (
     <article class="popover-hint">
       <h1>404</h1>
-      <p>{i18n(cfg.locale, "404")}</p>
+      <p>{i18n(cfg.locale).pages.error.notFound}</p>
     </article>
   )
 }