Removal of localStorage dependency v1

docs/store/synced.md

@@ -1,34 +1,49 @@
 # Synced Store
 
-Utility for creating Svelte stores that automatically persist to and restore from localStorage.
+Utility for creating Svelte stores that automatically persist to and restore from storage providers.
 
 ## Functions
 
-### synced(key, defaultValue)
+### synced(config)
 
-Creates a writable store that synchronizes with localStorage using JSON serialization.
+Creates a writable store that synchronizes with a storage provider using JSON serialization.
 
 **Parameters:**
-- `key` - localStorage key to store the value under
-- `defaultValue` - Default value if nothing exists in localStorage
+- `config` - Configuration object containing:
+  - `key` - Storage key to store the value under
+  - `storage` - Storage provider implementing the StorageProvider interface
+  - `defaultValue` - Default value if nothing exists in storage
 
-**Returns:** Writable Svelte store that persists changes to localStorage
+**Returns:** Writable Svelte store that persists changes to storage
 
 The store automatically:
-- Loads initial value from localStorage on creation
-- Saves any changes back to localStorage
-- Falls back to defaultValue if localStorage is empty or invalid
+- Loads initial value from storage on creation
+- Saves any changes back to storage
+- Falls back to defaultValue if storage is empty or invalid
+
+## Storage Provider Interface
+
+```typescript
+interface StorageProvider {
+  get: (key: string) => Promise<any>
+  set: (key: string, value: any) => Promise<void>
+}
+```
 
 ## Example
 
 ```typescript
-import {synced} from "@welshman/store"
+import {synced, localStorageProvider} from "@welshman/store"
 
-// Create a store that persists user preferences
-const userPreferences = synced("user-prefs", {
-  theme: "dark",
-  notifications: true,
-  language: "en"
+// Create a store that persists user preferences using localStorage
+const userPreferences = synced({
+  key: "user-prefs",
+  storage: localStorageProvider,
+  defaultValue: {
+    theme: "dark",
+    notifications: true,
+    language: "en"
+  }
 })
 
 // Use like any writable store
@@ -36,7 +51,7 @@ userPreferences.subscribe(prefs => {
   console.log("Preferences:", prefs)
 })
 
-// Update the store - automatically saves to localStorage
+// Update the store - automatically saves to storage
 userPreferences.update(prefs => ({
   ...prefs,
   theme: "light"