Publish API reference (Dokka HTML) to GitHub Pages (#32) (#40)

* docs: design spec for Dokka HTML API reference on GitHub Pages (#32)

* docs: implementation plan for Dokka API reference on GitHub Pages (#32)

* build: migrate Dokka 1.9.20 -> 2.2.0 (DGP v2) (#32)

* docs: aggregate all modules into one Dokka HTML site with source links (#32)

* docs: add Dokka source links to serialization/coroutines/compose modules (#32)

* ci: add docs workflow to deploy Dokka HTML to GitHub Pages (#32)

* docs: link the published API reference from the README (#32)

build.gradle.kts

@@ -59,6 +59,29 @@ repositories {
     mavenCentral()
 }
 
+dependencies {
+    // Include this module's own docs in the aggregation — DGP v2 requires the
+    // aggregating project to list itself explicitly.
+    dokka(project(":"))
+    dokka(project(":tree-structure-serialization"))
+    dokka(project(":tree-structure-coroutines"))
+    dokka(project(":tree-structure-compose"))
+}
+
+dokka {
+    moduleName.set("Tree Data Structure")
+    dokkaSourceSets.configureEach {
+        sourceLink {
+            localDirectory.set(projectDir.resolve("src"))
+            // For the root project projectDir == rootDir, so `module` is "" and links resolve to /blob/master/src.
+            val module = projectDir.relativeTo(rootDir).invariantSeparatorsPath
+            val prefix = if (module.isEmpty()) "" else "$module/"
+            remoteUrl("https://github.com/AdrianKuta/Tree-Data-Structure/blob/master/${prefix}src")
+            remoteLineSuffix.set("#L")
+        }
+    }
+}
+
 kotlin {
     explicitApi()
     jvmToolchain(21)