fix: Add nixpacks configuration for Astro deployment

dealplustech-astro/node_modules/mdast-util-gfm-strikethrough/index.d.ts

@@ -0,0 +1,19 @@
+export {
+  gfmStrikethroughFromMarkdown,
+  gfmStrikethroughToMarkdown
+} from './lib/index.js'
+
+// Add custom data tracked to turn a syntax tree into markdown.
+declare module 'mdast-util-to-markdown' {
+  interface ConstructNameMap {
+    /**
+     * Whole strikethrough.
+     *
+     * ```markdown
+     * > | ~~a~~
+     *     ^^^^^
+     * ```
+     */
+    strikethrough: 'strikethrough'
+  }
+}