add intro to SwiftJavaDocumentation index.md

Author: koloyyee

Sources/SwiftJavaDocumentation/Documentation.docc/index.md

@@ -11,7 +11,21 @@ Please refer to articles about the specific direction of interoperability you ar
 
 ### Getting started
 
-TODO: Some general intro
+**SwiftJava** provides Java and Swift interoperability with minimal overhead. It eliminates the complex, error-prone process of manually compiling Java classes to C headers for native access. With SwiftJava, developers can achieve a flexible, safe, and high-performance connection between the two languages.
+
+#### Interoperability promotes
+- Incremental adoption of Swift
+- Reuse of libraries
+- Support for ecosystem-specific build tools
+
+#### Tools
+- Swift Package: 
+    - JavaKit (Java -> Swift)
+- Java Library: 
+    - SwiftKit (Swift -> Java)
+- Tooling: 
+    - swift-java: command line tool [SwiftJavaCommandLineTool](#SwiftJavaCommandLineTool)
+    - Build tool integration: SwiftPM Plugin or Gradle [SwiftPMPlugin](#SwiftPMPlugin)
 
 If you prefer a video introduction, you may want to watch this 
 [Explore Swift and Java interoperability](https://www.youtube.com/watch?v=QSHO-GUGidA)