Merge service files of ComparatorProviders

Author: alexander-yevsyukov

buildSrc/src/main/kotlin/io/spine/gradle/publish/ShadowJarExts.kt

@@ -61,6 +61,11 @@ private object ServiceFiles {
      */
     private const val messageValidators = "$servicesDir/io.spine.validation.MessageValidator"
 
+    /**
+     * Comparator providers provided by the libraries.
+     */
+    private const val comparatorProviders = "$servicesDir/io.spine.compare.ComparatorProvider"
+
     /**
      * KSP symbol processor provider.
      */
@@ -80,6 +85,7 @@ private object ServiceFiles {
         descriptorSetReferences,
         optionProviders,
         messageValidators,
+        comparatorProviders,
         kspSymbolProcessorProviders,
         commandRoutingSetupClasses,
         eventRoutingSetupClasses,