refactor: Break apart monolithic configuration schema (#1977)

[skip ci]

src/config/schema/elements/stock/service-call.ts

@@ -0,0 +1,12 @@
+import { z } from 'zod';
+import { elementsBaseSchema } from '../base';
+
+// https://www.home-assistant.io/lovelace/picture-elements/#service-call-button
+export const serviceCallButtonSchema = elementsBaseSchema.extend({
+  type: z.literal('service-button'),
+
+  // Title is required for service button.
+  title: z.string(),
+  service: z.string(),
+  service_data: z.object({}).passthrough().optional(),
+});