fix: tsRestFetchApi content type parsing (#338)

* fix client logic

* changeset

* linting

Author: michaelangeloio

.changeset/four-days-wonder.md

@@ -0,0 +1,5 @@
+---
+'@ts-rest/core': minor
+---
+
+tsRestFetchApi should be more flexible when determining application/json content type header

libs/ts-rest/core/src/lib/client.ts

@@ -91,7 +91,7 @@ export const tsRestFetchApi: ApiFetcher = async ({
   });
   const contentType = result.headers.get('content-type');
 
-  if (contentType?.includes('application/json')) {
+  if (contentType?.includes("application/") && contentType?.includes('json')) {
     return {
       status: result.status,
       body: await result.json(),