Broken links fixed

[0xSandyy]

Related Issue

• Closes: https://github.com/kadenzipfel/smart-contract-vulnerabilities/issues/65

Checklist

• [x] I have read and followed the style guide

Describe the changes you've made:

I fixed all the borken links with similar links or new links referring to the same context and information.

Type of change

Select the appropriate checkbox:

• [x] Bug fix (fixing an issue with existing vulnerability data)
• [ ] New feature (adding a new vulnerability or category)
• [ ] Documentation update (improving existing information)

Additional Information

I had to add new links in some cases where previous broken links were not fixable due to the source being completely changed or source deleting the contents. Thus, I needed to add new links with different source but the content is similar to previous source.

Also, I deleted the reference to ./forcibly-sending-ether.md in dos-revert.md as it has not been implemented yet.