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`).

crates/owlen-cli/README.md

@@ -0,0 +1,15 @@
+# Owlen CLI
+
+This crate is the command-line entry point for the Owlen application.
+
+It is responsible for:
+
+-   Parsing command-line arguments.
+-   Loading the configuration.
+-   Initializing the providers.
+-   Starting the `owlen-tui` application.
+
+There are two binaries:
+
+-   `owlen`: The main chat application.
+-   `owlen-code`: A specialized version for code-related tasks.