Sets michael-rapp:java-util as an api dependency

> The plugin exposes two configurations that can be used to declare dependencies: api and implementation. The api configuration should be used to declare dependencies which are exported by the library API, whereas the implementation configuration should be used to declare dependencies which are internal to the component. More info [here](https://docs.gradle.org/current/userguide/java_library_plugin.html#sec:java_library_separation).

build.gradle

@@ -38,7 +38,7 @@ repositories {
 
 dependencies {
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$version_kotlin"
-    implementation "com.github.michael-rapp:java-util:$version_java_util"
+    api "com.github.michael-rapp:java-util:$version_java_util"
     implementation "org.slf4j:slf4j-api:$version_slf4j"
     testImplementation "org.jetbrains.kotlin:kotlin-test-junit:$version_kotlin"
     testImplementation "org.mockito:mockito-core:$version_mockito"
@@ -111,4 +111,4 @@ uploadArchives {
             }
         }
     }
-}
+}