added gradle build instructions

gradle/README.md

@@ -0,0 +1,37 @@
+# Build Scripts > Gradle
+
+## Gitlab Maven Repo
+
+```gradle
+// configure ids
+buildscript {
+    ext {
+        gitlabCiApiUrl = System.getenv("CI_API_V4_URL") ?: "https://gitlab.com/api/v4"
+        gitlabCiProjectId = System.getenv("CI_PROJECT_ID") ?: "TODO add project id for building outside CI here"
+    }
+}
+
+// add script
+apply from: 'https://raw.githubusercontent.com/dhswt/build-scripts/master/gradle/GitlabMavenRepo.gradle'
+
+// configure a gitlab as a source
+project {
+    repositories {
+        mavenCentral()
+        mavenLocal()
+        addGitlabGroupRepository(it, "<GROUP_NAME>", "<GROUP_ID>")
+    }
+}
+
+// publish to gitlab
+publishing {
+    repositories {
+        addGitlabPublishingRepository(it)
+    }
+    publications {
+        maven(MavenPublication) {
+            from components.java
+        }
+    }
+}
+```