Added store for the groups

src/stores/tag-groups-store.js

@@ -0,0 +1,12 @@
+import {writable} from "svelte/store";
+import TagGroup from "$entities/TagGroup.ts";
+
+/** @type {import('svelte/store').Writable<TagGroup[]>} */
+export const tagGroupsStore = writable([]);
+
+TagGroup
+  .readAll()
+  .then(groups => tagGroupsStore.set(groups))
+  .then(() => {
+    TagGroup.subscribe(groups => tagGroupsStore.set(groups));
+  });