feat(website): update home page to showcase CherryPick DI documentation

- Replaced the main action button text with 'Explore CherryPick Documentation 🍒' instead of 'Docusaurus Tutorial'.
- Updated the button link to target /docs/intro (main docs entry point).
- Changed <Layout> props:
  - Page title now uses project title only (siteConfig.title)
  - Added a CherryPick-related site description for better SEO and context.
- The homepage is now tailored to reflect CherryPick's purpose as a Dart & Flutter DI library instead of Docusaurus boilerplate.

website/docs/installation.md

@@ -0,0 +1,18 @@
+---
+sidebar_position: 2
+---
+
+# Installation
+
+Add to your `pubspec.yaml`:
+
+```yaml
+dependencies:
+  cherrypick: ^<latest_version>
+```
+
+Then run:
+
+```shell
+dart pub get
+```