Feature: Allow individual block to flash its trim when new update comes in

Can we add an option to allow client to configure a block's trim to be flashed when new event comes? Basically, some implementation of a block may have some slow update events and when there is an update, it's often more visually noticeable of the trim can flash using a different color, for example. If it can be an API that clients can access, that would be really helpful. Thanks!

The issue names no files or tests; start by locating the block update/event handling and the client-facing block API. Define how clients configure a trim flash, what update triggers it, and what completed behavior should look like, then identify tests for the new behavior.

Written by the indexing model from the issue text.