Fixes #1081 .

Describe your approach and how it fixes the issue.

Hi @kasparsd, could you use this PR?

The solution proposed by @lkraav seems to be in line with select2 documentation: https://select2.org/data-sources/ajax#rate-limiting-requests

Alternatively, it looks like quietMillis could have been a good option to use per documentation https://select2.github.io/select2/ :

This didn't work for me however.

I'm wondering if this line should also be taken out since it looks it serves no purpose for now: https://github.com/xwp/stream/blob/develop/ui/js/admin.js#L72

As for the time window, 0.5 seconds seem to be the sweet spot for me.

Checklist

• Project documentation has been updated to reflect the changes in this pull request, if applicable.
• I have tested the changes in the local development environment (see contributing.md).
• I have added phpunit tests.

Release Changelog

• Fix: Describe a bug fix included in this release.
• New: Describe a new feature in this release.

Release Checklist

• This pull request is to the master branch.
• Release version follows semantic versioning. Does it include breaking changes?
• Update changelog in readme.txt.
• Bump version in stream.php.
• Bump Stable tag in readme.txt.
• Bump version in classes/class-plugin.php.
• Draft a release on GitHub.

Change [ ] to [x] to mark the items as done.