On revalidation return 304 status to user but don't store it in the c…

…ache

e.g If we have a 200 response cached and then geta 304 on revalidate, we should return the 304 status code to the user on that request but subsequent requests that hit the cache should have a status code of 200.

src/index.js

@@ -34,7 +34,7 @@ const cacheableRequest = (request, cache) => (opts, cb) => {
 				const revalidatedPolicy = CachePolicy.fromObject(opts._revalidate.cachePolicy).revalidatedPolicy(opts, response);
 				if (!revalidatedPolicy.modified) {
 					const headers = revalidatedPolicy.policy.responseHeaders();
-					response = new Response(opts._revalidate.statusCode, headers, opts._revalidate.body, opts._revalidate.url);
+					response = new Response(response.statusCode, headers, opts._revalidate.body, opts._revalidate.url);
 					response.cachePolicy = revalidatedPolicy.policy;
 					response.fromCache = true;
 				}
@@ -52,7 +52,7 @@ const cacheableRequest = (request, cache) => (opts, cb) => {
 					const value = {
 						cachePolicy: response.cachePolicy.toObject(),
 						url: response.url,
-						statusCode: response.statusCode,
+						statusCode: response.fromCache ? opts._revalidate.statusCode : response.statusCode,
 						body
 					};
 					const ttl = response.cachePolicy.timeToLive();