Move collection to store module

packages/store/src/synced.ts

@@ -0,0 +1,11 @@
+import {writable} from "svelte/store"
+import {getJson, setJson} from "@welshman/lib"
+
+export const synced = <T>(key: string, defaultValue: T) => {
+  const init = getJson(key)
+  const store = writable<T>(init === undefined ? defaultValue : init)
+
+  store.subscribe((value: T) => setJson(key, value))
+
+  return store
+}