Provide a sync_status store

The `sync_status` would update every 10 seconds with the latest state of
all repos, to be displayed in the repo where needed.

src/lib/events.ts

@@ -1,3 +1,9 @@
+import type { SyncStatus } from "@bindings/repo/SyncStatus";
+
+import { SvelteMap } from "svelte/reactivity";
 import { writable } from "svelte/store";
 
 export const nodeRunning = writable<boolean>(false);
+export const syncStatus = writable<SvelteMap<string, SyncStatus>>(
+  new SvelteMap(),
+);