Add blog app scaffolding with remark plugins

apps/blog/astro.config.mjs

@@ -0,0 +1,19 @@
+import { defineConfig } from 'astro/config';
+import remarkDirective from 'remark-directive';
+import remarkGfm from 'remark-gfm';
+import remarkSlug from 'remark-slug';
+import remarkSmartypants from 'remark-smartypants';
+import remarkAside from './src/plugins/remark-aside.ts';
+
+export default defineConfig({
+  output: 'static',
+  markdown: {
+    remarkPlugins: [
+      remarkGfm,
+      remarkDirective,
+      remarkAside,
+      remarkSlug,
+      remarkSmartypants
+    ]
+  }
+});