feat: Allow user generated notifications (#2401)

src/config/schema/common/icon.ts

@@ -0,0 +1,18 @@
+import { z } from 'zod';
+
+export const iconSchema = z.object({
+  // MDI icon name (e.g. 'mdi:star').
+  icon: z.string().optional(),
+
+  // HA entity whose icon will be used when `icon` is not set.
+  entity: z.string().optional(),
+
+  // Whether to tint the icon color based on the entity's state.
+  stateColor: z.boolean().optional(),
+});
+export type Icon = z.infer<typeof iconSchema>;
+
+// Extended internally to include a fallback icon that is not user-configurable.
+export interface InternalIcon extends Icon {
+  fallback?: string;
+}