lost code
Fixed the wrong translation.

Fixed the wrong translation of its.
make gitbook
make gitbook
add translator info
add translator info
Merge pull request #168 from yulingtianxia/develop

update optional chaining
Merge pull request #166 from twlkyao/patch-1

Fixed the wrong translation.
Update README.md

add to 02 -17 optional chaining.
fix conflict
Merge branch 'limingit-gh-pages' into gh-pages
Merge branch 'gh-pages' of https://github.com/numbbbbb/the-swift-programming-language-in-chinese into gh-pages
make gitbook
Merge pull request #169 from Jasonbroker/patch-1

Update README.md
correct the wrong "half-closed loop"