Merge pull request #420 from jingliancui/main

add requirement of xcode version to readme

Author: stephen-hawley

README.md

@@ -12,6 +12,10 @@ Check out our [quickstart guide](QUICKSTART.md) to build and run the tool locall
 
 The packaging of BTFS is still evolving, and we expect to provide a binding project style interface to make this process easier in the future.
 
+## Caution ❗
+
+In order to contribute to Binding-Tools-For-Swift, you will need Xcode 10.2 !
+
 ## Current Status
 
 ### What Binds?