refactor: Break apart monolithic configuration schema (#1977)

[skip ci]

src/config/schema/timeline.ts

@@ -0,0 +1,19 @@
+import { z } from 'zod';
+import { thumbnailsControlSchema } from './common/controls/thumbnails';
+import {
+  timelineConfigDefault,
+  timelineCoreConfigSchema,
+} from './common/controls/timeline';
+
+export const timelineConfigSchema = timelineCoreConfigSchema
+  .extend({
+    controls: z
+      .object({
+        thumbnails: thumbnailsControlSchema.default(
+          timelineConfigDefault.controls.thumbnails,
+        ),
+      })
+      .default(timelineConfigDefault.controls),
+  })
+  .default(timelineConfigDefault);
+export type TimelineConfig = z.infer<typeof timelineConfigSchema>;