fix: Add nixpacks configuration for Astro deployment

dealplustech-astro/node_modules/iron-webcrypto/dist/example.js

@@ -0,0 +1,19 @@
+const { webcrypto } = require('node:crypto')
+const Iron = require('iron-webcrypto')
+
+const obj = {
+  a: 1,
+  b: 2,
+  c: [3, 4, 5],
+  d: {
+    e: 'f'
+  }
+}
+
+const password = 'a_password_having_at_least_32_chars'
+
+const sealed = await Iron.seal(webcrypto, obj, password, Iron.defaults)
+console.log({ sealed })
+
+const unsealed = await Iron.unseal(webcrypto, sealed, password, Iron.defaults)
+console.log({ unsealed })