Add License to Vector Math for 3D Computer Graphics

[MananJain-IITJ]

What does this PR do?

Add info based on #11355

For resources

Description

1. Vector Math for 3D Computer Graphics -> License found at the end of website

Why is this valuable (or not)?

This information clarifies the licensing for this resource, ensuring users understand the terms under which they can use, modify, and distribute the content.

How do we know it's really free?

N/A

For book lists, is it a book? For course lists, is it a course? etc.

N/A

Checklist:

• Read our contributing guidelines.
• Search for duplicates.
• Include author(s) and platform where appropriate.
• Put lists in alphabetical order, correct spacing.
• Add needed indications (PDF, access notes, under construction).
• Used an informative name for this pull request.

Follow-up

• Check the status of GitHub Actions and resolve any reported warnings!