Fix .d.ts resolution-mode

Author: drwpow

.changeset/calm-walls-love.md

@@ -0,0 +1,5 @@
+---
+"openapi-typescript": patch
+---
+
+Fix .d.ts module resolution typings

packages/openapi-typescript/tsconfig.build.json

@@ -1,4 +1,8 @@
 {
   "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "module": "ES2022",
+    "moduleResolution": "Node"
+  },
   "exclude": ["scripts", "test", "*.ts"]
 }