feat: add configuration and default image for blog posts

- Introduced a new configuration file to centralize author information and default image settings for blog posts.
- Added a default image path in the blog post configuration for improved content presentation.
- Updated blog post schema to utilize the new configuration for author details, enhancing structured data representation.

src/content/config.ts

@@ -3,13 +3,13 @@ import { defineCollection, z } from "astro:content";
 const blog = defineCollection({
 	type: "content",
 	schema: z.object({
-		author: z.string(),
 		basedOn: z.optional(z.string()),
 		dateModified: z.coerce.date(),
 		datePublished: z.coerce.date(),
 		description: z.string(),
 		draft: z.optional(z.boolean()),
 		lang: z.string(),
+		preview: z.optional(z.string()),
 		title: z.string(),
 	}),
 });