feat: Add in-app documentation system

Phase 1: Core Documentation
- Created docs/ folder with 8 markdown documentation files
- Getting Started, Installation, Troubleshooting, FAQ
- Configuration docs (Appearance, SPA Mode)
- Feature docs (Shop, Checkout)
- PHP registry with filter hook for addon extensibility

Phase 2: Documentation Viewer
- DocsController.php with REST API endpoints
- GET /woonoow/v1/docs - List all docs (with addon hook)
- GET /woonoow/v1/docs/{slug} - Get document content
- Admin SPA /help route with sidebar navigation
- Markdown rendering with react-markdown
- Added Help & Docs to More page for mobile access

Filter Hook: woonoow_docs_registry
Addons can register their own documentation sections.

docs/getting-started.md

@@ -0,0 +1,54 @@
+# Getting Started with WooNooW
+
+Welcome to WooNooW! This guide will help you get up and running quickly.
+
+## What is WooNooW?
+
+WooNooW transforms your WooCommerce store into a modern, fast Single Page Application (SPA). It provides:
+
+- ⚡ **Instant Page Loads** - No page refreshes between navigation
+- 🎨 **Modern UI** - Beautiful, responsive design out of the box
+- 🛠 **Easy Customization** - Configure colors, fonts, and layout from admin
+- 📱 **Mobile-First** - Optimized for all devices
+
+## Quick Setup (3 Steps)
+
+### Step 1: Activate the Plugin
+
+After installing WooNooW, activate it from **Plugins → Installed Plugins**.
+
+The plugin will automatically:
+- Create a "Store" page for the SPA
+- Configure basic settings
+
+### Step 2: Access Admin Dashboard
+
+Go to **WooNooW** in your WordPress admin menu.
+
+You'll see the admin dashboard with:
+- Orders management
+- Settings configuration
+- Appearance customization
+
+### Step 3: Configure Your Store
+
+Navigate to **Appearance** settings to:
+
+1. **Upload your logo**
+2. **Set brand colors** (primary, secondary, accent)
+3. **Choose fonts** for headings and body text
+4. **Configure SPA mode** (Full or Disabled)
+
+## Next Steps
+
+- [Installation Guide](installation) - Detailed installation instructions
+- [Appearance Settings](configuration/appearance) - Customize your store's look
+- [SPA Mode](configuration/spa-mode) - Understand Full vs Disabled mode
+- [Troubleshooting](troubleshooting) - Common issues and solutions
+
+## Need Help?
+
+If you encounter any issues:
+1. Check the [Troubleshooting](troubleshooting) guide
+2. Review the [FAQ](faq)
+3. Contact support with your WordPress and WooCommerce versions