Type of issue

Feature request

Description

Many adapters may want to write to the shared storage api. Currently they can use https://github.com/WICG/shared-storage/blob/main/README.md#from-response-headers to write from their response headers, but that may induce them to create network traffic just to trigger the method. We should allow writes to shared storage from an adapter, particularly to support the case when network traffic would not otherwise occur and values are calculated subsequent to existing network traffic