Downgrade dokka

The latest version does not support multi-platform projects.

build.gradle.kts

@@ -45,13 +45,17 @@ subprojects {
         plugins.withType<KotlinMultiplatformPluginWrapper> {
             apply(plugin = "org.jetbrains.dokka")
 
-            val dokkaJavadoc by tasks.existing(DokkaTask::class)
+            val dokka by tasks.existing(DokkaTask::class) {
+                outputFormat = "javadoc"
+                outputDirectory = "$buildDir/docs/javadoc"
+            }
 
             val javadocJar by tasks.registering(Jar::class) {
                 group = LifecycleBasePlugin.BUILD_GROUP
                 description = "Assembles a jar archive containing the Javadoc API documentation."
                 archiveClassifier.set("javadoc")
-                from(dokkaJavadoc)
+                dependsOn(dokka)
+                from(dokka.get().outputDirectory)
             }
 
             configure<KotlinMultiplatformExtension> {

buildSrc/src/main/kotlin/Versions.kt

@@ -1,5 +1,5 @@
 object Versions {
-    const val dokka = "1.4.20"
+    const val dokka = "0.10.1"
     const val kotlin = "1.4.21-2"
     const val kotlinBenchmark = "0.2.0-dev-20"
     const val kotlinCoroutines = "1.4.2"