[FEATURE REQUEST] automatically detect duplicate issues

### I have searched through the issues and didn't find my problem.

- [X] Confirm

### Problem

Every now and then a few duplicate issues pop up. Usually they are issues for adding an icon that has already been suggested in another issue. These need to be manually labeled as `duplicate` and closed by maintainers.

It would be better if a bot did this for us once it finds duplicates.

### Possible Solution

Have a GitHub Action which triggers when a new issue is created, that marks issues as duplicates.

It should be manageable to do it for `feature:icon` issues since we can just match the title almost 1:1, but for other types of issues we'll have to do keyword matching, and instead assign or tag a maintainer, since we can't be sure if it's a duplicate, or just a similar title.

Hopefully we can use an existing GitHub Action for this, but in case we can't here's how we can go about creating one.

The action should do the following:
1. Run on issue creation
2. Get title of issue
3. Search through existing issues and extract the titles
4. See if it finds issues that closely match the title. If there's a close match, tag or assign it to a contributor.
5. See if the title is an exact match, in which case the issue should be closed and labeled `duolicate`

### Additional information

This might be a bit overkill, but I think at least the functionality of closing exact matches would be nice, and relatively easy to implement.

Looking for feedback here though, since I'm really not sure how worth it this is.