Add module documentation and enhance Dokka configuration (#261)

##  #252 Add module documentation and enhance Dokka configuration

## How Has This Been Tested?

`./gradlew :docs:dokkaGenerate`

## Changes

- Add workflow to build and publish API documentation with Dokka
- Introduce `.github/workflows/apidocs.yaml` to build and deploy API
docs on `main` and release events.
  - Configure Gradle for Dokka builds and update project dependencies.
  - Include `:docs` module in project settings.
- Introduce `Module.md` for `kotlin-sdk-server`, `kotlin-sdk-client`,
and `kotlin-sdk-core` modules.
- Update `.gitignore` to include `.idea/icon.png` and add placeholder
icon files
- Remove outdated documentation HTML files

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [x] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [x] I have added or updated documentation as needed

## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->

---------

Co-authored-by: devcrocod <devcrocod@gmail.com>

buildSrc/src/main/kotlin/mcp.dokka.gradle.kts

@@ -5,9 +5,14 @@ plugins {
 }
 
 dokka {
-    moduleName.set("MCP Kotlin SDK - ${project.name}")
 
     dokkaSourceSets.configureEach {
+        includes.from("Module.md")
+
+        pluginsConfiguration.html {
+            footerMessage = "Copyright © 2024-2025 Anthropic, PBC"
+        }
+
         sourceLink {
             localDirectory = projectDir.resolve("src")
             remoteUrl("https://github.com/modelcontextprotocol/kotlin-sdk/tree/main/${project.name}/src")
@@ -15,9 +20,20 @@ dokka {
         }
 
         documentedVisibilities(VisibilityModifier.Public)
-    }
 
-    dokkaPublications.html {
-        outputDirectory = rootProject.layout.projectDirectory.dir("docs/${project.name}")
+        externalDocumentationLinks.register("ktor-client") {
+            url("https://api.ktor.io/ktor-client/")
+            packageListUrl("https://api.ktor.io/package-list")
+        }
+
+        externalDocumentationLinks.register("kotlinx-coroutines") {
+            url("https://kotlinlang.org/api/kotlinx.coroutines/")
+            packageListUrl("https://kotlinlang.org/api/kotlinx.coroutines/package-list")
+        }
+
+        externalDocumentationLinks.register("kotlinx-serialization") {
+            url("https://kotlinlang.org/api/kotlinx.serialization/")
+            packageListUrl("https://kotlinlang.org/api/kotlinx.serialization/package-list")
+        }
     }
-}
+}