[jextract/jni] update docs about throwing and optional init and add tests - #426

[jextract/jni] update docs about throwing and optional init and add tests#426

ktoso merged 1 commit into

swiftlang:mainswiftlang/swift-java:mainfrom

madsodgaard:update-init-docsmadsodgaard/swift-java:update-init-docsCopy head branch name to clipboard