add delete to admin panel

src/util/state.ts

@@ -0,0 +1,24 @@
+import type { Writable } from 'svelte/store';
+
+export function addToWritableArray<T>(writable: Writable<T[]>, t: T) {
+  writable.update((old) => {
+    old.push(t);
+    return old;
+  });
+}
+
+export function updateWritableArray<T>(writable: Writable<T[]>, t: T, cmp: (t: T) => boolean) {
+  writable.update((old) => {
+    const index = old.findIndex(cmp);
+    old[index] = t;
+    return old;
+  });
+}
+
+export function deleteFromWritableArray<T>(writable: Writable<T[]>, cmp: (t: T) => boolean) {
+  writable.update((old) => {
+    const index = old.findIndex(cmp);
+    old.splice(index, 1);
+    return old;
+  });
+}