[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/.readthedocs.yaml

@@ -0,0 +1,17 @@
+# .readthedocs.yaml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "mambaforge-22.9" # https://docs.readthedocs.io/en/stable/guides/conda.html#making-builds-faster-with-mamba
+
+mkdocs:
+  configuration: "docs/locales/zh/mkdocs.yml"
+
+conda:
+  environment: "docs/environment.yml"