Second try at configuring i18n for docsify and gitbook (#4531)

* add zh-cn readme

* edit readme

* Round 1 of edits

- Mandarin translation of QMK products is off, best to use the English name.
- Fix some terminology and grammar.

* trying re-translating the first paragraph

* add fallback langurages

* Create LANGS.md

* Rename docs/zh-cn/README.md to docs/zh/README.md

* Update LANGS.md

* Update index.html

docs/index.html

@@ -25,7 +25,8 @@
         placeholder: 'Search Documentation...',
         noData: 'We could not find any documents matching your search.',
         depth: 6
-      }
+      },
+      fallbackLanguages: ['zh']
     }
   </script>
   <script src="//unpkg.com/docsify/lib/docsify.min.js"></script>