misc: Add note regarding fetch API rethrow (#2740)

Author: kamilogorek

packages/utils/src/instrument.ts

@@ -169,6 +169,9 @@ function instrumentFetch(): void {
             endTimestamp: Date.now(),
             error,
           });
+          // NOTE: If you are a Sentry user, and you are seeing this stack frame,
+          //       it means the sentry.javascript SDK caught an error invoking your application code.
+          //       This is expected behavior and NOT indicative of a bug with sentry.javascript.
           throw error;
         },
       );