PROBLEM
Our merge conflict notification bot advises users they have a merge conflict, but it does not notify users they have a merge conflict caused by main updating.

Sometimes, main updates e.g. a user adds a new issue with a new changelog entry, and this causes a merge conflict with the existing PR's.

The existing PR's have had no changes, but now they have a merge conflict.

Currently, our merge conflict notification will only run if the PR itself updates:
on:
pull_request_target:
types: [opened, synchronize, reopened]

Therefore, if main updates and this causes a merge conflict with the PR - nothing will be sent - even if there is now a merge conflict.

SOLUTION
Change .github/workflows/merge-conflict-bot.yml to recognise if there is a merge conflict triggered when main updates

e.g.
on:
push:
branches:
- main

We should double check it correctly identifies merge conflicts in that scenario