fix(#5): fix crash after upgrading to Spring Boot 2.3

Author: BlasiusSecundus

graphql-kickstart-spring-boot-autoconfigure-graphql-annotations/build.gradle

@@ -6,6 +6,7 @@ dependencies {
     api "io.github.graphql-java:graphql-java-annotations:$LIB_GRAPHQL_ANNOTATIONS_VER"
     implementation "org.reflections:reflections:$LIB_REFLECTIONS_VER"
     implementation "org.springframework.boot:spring-boot-autoconfigure"
+    implementation "org.springframework.boot:spring-boot-starter-validation"
     annotationProcessor "org.springframework.boot:spring-boot-configuration-processor"
 
     testImplementation "org.springframework.boot:spring-boot-starter-test"