Add comprehensive documentation and examples for Owlen architecture and usage

- Include detailed architecture overview in `docs/architecture.md`.
- Add `docs/configuration.md`, detailing configuration file structure and settings.
- Provide a step-by-step provider implementation guide in `docs/provider-implementation.md`.
- Add frequently asked questions (FAQ) document in `docs/faq.md`.
- Create `docs/migration-guide.md` for future breaking changes and version upgrades.
- Introduce new examples in `examples/` showcasing basic chat, custom providers, and theming.
- Add a changelog (`CHANGELOG.md`) for tracking significant changes.
- Provide contribution guidelines (`CONTRIBUTING.md`) and a Code of Conduct (`CODE_OF_CONDUCT.md`).

examples/session_management.rs

@@ -0,0 +1,28 @@
+// This example demonstrates how to use the session controller.
+
+use owlen_core::session::Session;
+
+fn main() {
+    // Create a new session.
+    let mut session = Session::new("my-session");
+    println!("Created new session: {}", session.name);
+
+    // Add messages to the session.
+    session.add_message("user", "Hello, Owlen!");
+    session.add_message("bot", "Hello, user! How can I help you today?");
+
+    // Get the messages from the session.
+    let messages = session.get_messages();
+    println!("\nMessages in session:");
+    for message in messages {
+        println!("  {}: {}", message.role, message.content);
+    }
+
+    // Clear the session.
+    session.clear_messages();
+    println!("\nSession cleared.");
+
+    let messages_after_clear = session.get_messages();
+    println!("Messages in session after clear: {}", messages_after_clear.len());
+}
+