Publish gradle attributes for AndroidX compatibility

These attributes are required when importing our artifacts into
androidx-main in order to generate reference documentation (JavaDoc and
KDoc).

#minor-release

PiperOrigin-RevId: 504502555

publish.gradle

@@ -26,10 +26,26 @@ afterEvaluate {
             publications {
                 release(MavenPublication) {
                     from components.release
-                    artifact androidSourcesJar
                     groupId = 'androidx.media3'
                     artifactId = findProperty('releaseArtifactId') ?: ''
                     version = findProperty('releaseVersion') ?: ''
+                    configurations.create("sourcesElement") { variant ->
+                        variant.visible = false
+                        variant.canBeResolved = false
+                        variant.attributes.attribute(
+                            Usage.USAGE_ATTRIBUTE,
+                            project.objects.named(Usage, Usage.JAVA_RUNTIME))
+                        variant.attributes.attribute(
+                            Category.CATEGORY_ATTRIBUTE,
+                            project.objects.named(Category, Category.DOCUMENTATION))
+                        variant.attributes.attribute(
+                            Bundling.BUNDLING_ATTRIBUTE,
+                            project.objects.named(Bundling, Bundling.EXTERNAL))
+                        variant.attributes.attribute(
+                            DocsType.DOCS_TYPE_ATTRIBUTE,
+                            project.objects.named(DocsType, DocsType.SOURCES))
+                        variant.outgoing.artifact(androidSourcesJar)
+                        components.release.addVariantsFromConfiguration(variant) {}
                     pom {
                         name =
                             findProperty('releaseName')