add docs

Author: zeitlinger

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/resources/ResourceCustomizerProvider.java

@@ -27,6 +27,10 @@
 @AutoService(DeclarativeConfigurationCustomizerProvider.class)
 public class ResourceCustomizerProvider implements DeclarativeConfigurationCustomizerProvider {
 
+  // distribution: adds "distro.name" and "distro.version" attributes
+  // (DistroComponentProvider in this package)
+  // service: adds "service.name" and "service.instance.id" attributes
+  // (https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk-extensions/incubator/src/main/java/io/opentelemetry/sdk/extension/incubator/fileconfig/ServiceResourceDetector.java)
   private static final List<String> REQUIRED_DETECTORS = Arrays.asList("distribution", "service");
 
   @Override