update astro config to move deprecated fields

Author: carsakiller

astro.config.mjs

@@ -4,6 +4,7 @@ import mdx from "@astrojs/mdx";
 import { modifiedTime } from "./src/plugins/modifiedTime.mjs";
 import rehypeMdxCodeProps from "rehype-mdx-code-props";
 import mermaid from "astro-mermaid";
+import { unified } from "@astrojs/markdown-remark";
 
 // https://astro.build/config
 export default defineConfig({
@@ -30,8 +31,10 @@ export default defineConfig({
     },
   ],
   markdown: {
-    rehypePlugins: [rehypeMdxCodeProps],
-    remarkPlugins: [modifiedTime],
+    processor: unified({
+      rehypePlugins: [rehypeMdxCodeProps],
+      remarkPlugins: [modifiedTime],
+    }),
   },
   trailingSlash: "always",
 });