fix: Add nixpacks configuration for Astro deployment

dealplustech-astro/node_modules/is-plain-obj/index.d.ts

@@ -0,0 +1,35 @@
+/**
+Check if a value is a plain object.
+
+An object is plain if it's created by either `{}`, `new Object()`, or `Object.create(null)`.
+
+@example
+```
+import isPlainObject from 'is-plain-obj';
+import {runInNewContext} from 'node:vm';
+
+isPlainObject({foo: 'bar'});
+//=> true
+
+isPlainObject(new Object());
+//=> true
+
+isPlainObject(Object.create(null));
+//=> true
+
+// This works across realms
+isPlainObject(runInNewContext('({})'));
+//=> true
+
+isPlainObject([1, 2, 3]);
+//=> false
+
+class Unicorn {}
+isPlainObject(new Unicorn());
+//=> false
+
+isPlainObject(Math);
+//=> false
+```
+*/
+export default function isPlainObject<Value>(value: unknown): value is Record<PropertyKey, Value>;