[zh] start Simplified Chinese translation

add
- /index.rst
- /contributing.rst
- /contributing/
[zh] align table cell boundary (| and +), giving Chinese characters same space as English characters instead of double bytes vs single byte.
Update controllers.rst, deprecation of $title_for_layout
Update controllers.rst
Merge pull request #1719 from mstra001/patch-1

Update controllers.rst, deprecation of $title_for_layout
[zh] add/update build tooling files for language zh
[zh] re-wrap at column 80, giving Chinese characters the same space as English characters instead of double bytes vs single byte.
[fr] fix typo in french translation
Merge pull request #1712 from blackpuppy/zh

[zh] start Simplified Chinese translation
Fix table formatting in zh translation.
[zh] fix sphinx build error: keep class attribute value for "container" directive in the original text
[zh] follow en update
[zh] add /zh/contents.rst to fix sphinx build warning
Merge pull request #1721 from blackpuppy/zh

[zh] fix sphinx build errors from last pull request #1712
[zh] add /zh/epub-contents.rst to fix sphinx build error
[zh] add /zh/pdf-contents.rst to fix sphinx build error
[zh] fix lang=en error in *contents.rst files
[zh] fix sphinx build warnings about nonexisting document in *contents.rst
[zh] try to fix sphinx warnings in build #1986
Merge pull request #1722 from blackpuppy/zh

[zh] fix sphinx build errors from last pull request #1721