Updated the broken links under "Implementing a Search Engine" section

Description

Since the original owner no longer seems to maintain the website and the website no longer works, I added Internet Archive links (web.archive.org).

Motivation and Context

Works as a makeshift solution until a better solution is found
Fixes #380

How Has This Been Tested?

All the three links have been changed and are in a working condition.
They correctly navigate a snapshot of the original website taken by the Internet Archive (web.archive.org)

Types of changes

• Content Update (change which fixes an issue or updates an already existing submission)
• New Article (change which adds functionality)
• Documentation change

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have made checks to ensure URLs and other resources are valid