[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.
[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.
Merge pull request #1712 from blackpuppy/zh

[zh] start Simplified Chinese translation