fix: Add nixpacks configuration for Astro deployment

dealplustech-astro/node_modules/regex/dist/cjs/backcompat.d.ts

@@ -0,0 +1,8 @@
+/**
+Applies flag v rules when using flag u, for forward compatibility.
+Assumes flag u and doesn't worry about syntax errors that are caught by it.
+@param {string} expression
+@returns {PluginResult}
+*/
+export function backcompatPlugin(expression: string): PluginResult;
+import type { PluginResult } from './regex.js';