AUDIO: Added sounds for medieval keys

[Zungrysoft]

Description of Changes

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Added sounds for medieval keys. Three new sounds:

• misc/medkey.wav - Picking up the key.
• doors/medtry.wav - Failing to open a key door.
• doors/meduse.wav - Opening a key door.

Audio Sample

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https://github.com/user-attachments/assets/a65c2e18-76ba-4d18-8939-2123b8367cbd

Checklist

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• [x] I have read the LibreQuake contribution guidelines
• [x] I have thoroughly tested my changes to the best of my ability
• [x] I confirm I have not contributed anything that would impact LibreQuake's licensing and usage
• [ ] This Pull Request fixes a critical issue that should be reviewed and merged as soon as possible