Add Chinese translation

[greyli]

Language: Chinese

Hi, my name is Grey Li. I'm a maintainer of Flask. I request to add the Chinese translation of Flask's documentation.

Initial tasks

• Generate a repository from flaskcwg/translation-template, include all branches.
• Name your repository as flask-docs-<lang code>, for example, flask-docs-es.
• Add pallets/flask as upstream remote, then update:

$ git remote add upstream https://github.com/pallets/flask
$ git fetch upstream
$ git merge upstream/2.0.x

• Setup the virtual environment, install the requirements:

$ python -m pip install --upgrade pip setuptools
$ pip install -r requirements/dev.txt
$ pip install sphinx-intl
$ pip install -e .
$ pre-commit install

• Generate the .pot and .po files (replace <lang code> with your language code):

$ cd docs
$ make gettext  # use ".\make.bat gettext" on Windows
$ sphinx-intl update -p _build/gettext -l <lang code>

• Replace the <LANG> in the README, the language config, and the
  html_search_language config in docs/conf.py with your language code.
  Update the .po file examples.
• Setup ReadtheDocs to connect your repository, use flask-<lang code> as the subdomain, set the default version to the main branch, and enable the "single version" mode.
• Update the title, and all the <UPDATE THIS> placeholders in README.md and docs/conf.py. You can update the README to add more format or translate tips for your language.
• Update the Language-Team value in all .po files.
• Translate html_title and project links in the docs/conf.py file.
• Translate the docs/index file (you can make a localized logo for the index page).
• Translate the docs/foreword file.
• Translate the docs/advanced-foreword file.
• Translate the docs/installation file.
• Translate the docs/quickstart file.
• Translate the "Tutorial" part of the docs.
• Switch the repository into the flaskcwg organization.

Public

Tasks after the repository is switched into flaskcwg:

• Add a new language entry to the README.
• Add a new language entry to translations page.

Maintenance

Tasks when the whole documentation is translated:

• Create a 2.0.x branch, set it as default version on ReadtheDocs.
• Rewrite the contributing guide in the README of the translation repository, encourage people to fetch upstream and update docs (see details below).
• Rename the section "Translation To-do List" to "Translators". You can also add
  a "Reviewers" section.
• Switch the docs into http://flask.palletsprojects.com/.

You should sync documentation updates from Flask periodically:

$ git fetch upstream
$ git merge upstream/main
$ cd docs
$ make gettext  # use ".\make.bat gettext" on Windows
$ sphinx-intl update -p _build/gettext

Then update the translation for new changes.