Slack Notification - Issue Error Message Customization

### Problem Statement

This request is for the Slack <> Sentry Slack Notification. I'm using the Sentry UE5 plugin to submit Sentry events.


As a user, I'd like to be able to customize the issue error message that appears in the code block in the Slack notification. By default, the message is always set to something similar to `Fatal Error: unknown 0x000bdb30 / 0x7ffe3bae5b0c`

I'd like to overwrite that fatal error message with text that's more user friendly. I do know the 'notes' field exists, however that field is not formatted as a code block so it's harder for users to read at a glance.

### Solution Brainstorm

_No response_

### Product Area

Issues