docs: update README examples and add implementation plan

- Update README.md examples to use new declarative API
- Replace viewer.loadItems() with viewer.data().into()
- Add favicon to example playground
- Add API simplification implementation plan

Author: Max Carlson

WebSites/spacecraft-viewer/README.md

@@ -46,10 +46,17 @@ import { Viewer } from 'spacecraft-viewer'
 const canvas = document.getElementById('viewer')
 const viewer = new Viewer(canvas)
 
-viewer.loadItems([
-  {id: 'item-1', title: 'First Item'},
-  {id: 'item-2', title: 'Second Item'}
-])
+// Use the declarative API
+viewer
+  .data([
+    {id: 'item-1', title: 'First Item'},
+    {id: 'item-2', title: 'Second Item'}
+  ])
+  .into('items', {
+    layout: 'grid',
+    columns: 5,
+    spacing: 2
+  })
 
 viewer.start()
 ```
@@ -181,7 +188,7 @@ const transport = new SupabaseTransport({
 await transport.connect()
 
 const viewer = new Viewer(canvas, { transport })
-viewer.loadItems(items)
+viewer.data(items).into('items', { layout: 'grid' })
 viewer.start()
 ```