feat: add changeset

according to SEMVER spec, this must be a minor update:
> Minor version Y (x.Y.z | x > 0) MUST be incremented if new, backward compatible functionality is introduced to the public API.

.changeset/ten-poems-appear.md

@@ -0,0 +1,5 @@
+---
+"openapi-zod-client": minor
+---
+
+Add `schemaRefiner` option to allow refining the OpenAPI schema before its converted to a Zod schema