docs: Update guillotine packer documentation link

[tymokvo]

PR Details

• Replace link in GuillotinePacker documentation

Description

While browsing the Core.Mathematics namespace, I noticed that the link to http://clb.demon.fi/files/RectangleBinPack.pdf seems to have rotted. After a bit of googling, I think I was able to find the author's github and a link to the PDF there.

Related Issue

None, just a documentation change.

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My change requires a change to the documentation.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have built and run the editor to try this change out.

[Eideren]

Thanks !