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`).

docs/migration-guide.md

@@ -0,0 +1,34 @@
+# Migration Guide
+
+This guide documents breaking changes between versions of Owlen and provides instructions on how to migrate your configuration or usage.
+
+As Owlen is currently in its alpha phase (pre-v1.0), breaking changes may occur more frequently. We will do our best to document them here.
+
+--- 
+
+## Migrating from v0.1.x to v0.2.x (Example)
+
+*This is a template for a future migration. No breaking changes have occurred yet.*
+
+Version 0.2.0 introduces a new configuration structure for providers. 
+
+### Configuration File Changes
+
+Previously, your `config.toml` might have looked like this:
+
+```toml
+# old config.toml (pre-v0.2.0)
+ollama_base_url = "http://localhost:11434"
+```
+
+In v0.2.0, all provider settings are now nested under a `[providers]` table. You will need to update your `config.toml` to the new format:
+
+```toml
+# new config.toml (v0.2.0+)
+[providers.ollama]
+base_url = "http://localhost:11434"
+```
+
+### Action Required
+
+Update your `~/.config/owlen/config.toml` to match the new structure. If you do not, Owlen will fall back to its default provider configuration.