Add notice at the beginning of issue templates asking reporters to check for duplicates first
What does this MR do?
This adds a notice to ask reporters to check for duplicates before creating an issue.
Are there points in the code the reviewer needs to double check?
People might not remove the notice. I thought of putting it in a <details></details>
block but then readers would be tempted to open them to check it it's the notice or not, so it would be counter-productive. I think if people don't remove the notice, that's probably not a big deal...
Why was this MR needed?
Because we get a lot of duplicates.
Closes #31549 (closed)