fix: Add nixpacks configuration for Astro deployment

dealplustech-astro/node_modules/mdast-util-to-markdown/lib/util/format-heading-as-setext.d.ts

@@ -0,0 +1,9 @@
+/**
+ * @param {Heading} node
+ * @param {State} state
+ * @returns {boolean}
+ */
+export function formatHeadingAsSetext(node: Heading, state: State): boolean;
+import type { Heading } from 'mdast';
+import type { State } from 'mdast-util-to-markdown';
+//# sourceMappingURL=format-heading-as-setext.d.ts.map