update publication scripts

bot/publish.gradle

@@ -6,6 +6,10 @@ task javadocJar(type: Jar) {
     from javadoc
     classifier = 'javadoc'
 }
+task sourcesJar(type: Jar) {
+    from sourceSets.main.allSource
+    classifier = 'sources'
+}
 
 publishing {
     publications {
@@ -13,6 +17,7 @@ publishing {
             from components.java
 
             artifact javadocJar
+            artifact sourcesJar
 
             pom {
                 resolveStrategy = Closure.DELEGATE_FIRST