Fix broken links

Author: nakamura-to

README.md

@@ -57,5 +57,5 @@ kapt {
 Example build.gradle
 --------------------
 
-- Java: https://github.com/domaframework/simple-examples/blob/master/build.gradle
-- Kotlin: https://github.com/domaframework/kotlin-sample/blob/master/build.gradle
+- Java: https://github.com/domaframework/simple-examples/blob/master/build.gradle.kts
+- Kotlin: https://github.com/domaframework/kotlin-sample/blob/master/build.gradle.kts