[docs] add zh docs (#3507)

* [docs] add zh docs

* [docs] add lang dropdown

* [docs] update mkdocs zh config

* [docs] migrate assets

* [docs] update overrides dir in mkdocs zh config

* [docs] exclude locales director in main mkdocs config

* [docs] rename assets to public to avoid conflicting with template

* [docs] extra_css change followup

* [docs] add theme.palette.toggle.icon back into mkdocs zh config

* [docs] fix zh readme reference + migrate language-specific repo markdown to docs

* [docs] translate remaining repo docs + update reference

* [docs] update zh index.md reference

* [docs/zh] wording alignment

docs/locales/zh/getting_started/releases.md

@@ -0,0 +1,11 @@
+# 发行版
+
+GoToSocial 可以通过多种方式进行安装。我们发布官方的二进制文件以及容器镜像。
+
+有许多第三方软件包由不同的发行版维护，一些用户还创建了额外的部署工具，以便你可以轻松地自行部署 GoToSocial。
+
+{%
+  include "../repo/README.md"
+  start='<!--releases-start-->'
+  end='<!--releases-end-->'
+%}