fix: handle http protocol capitalization when checking links

[dan-mba]

Changes proposed

It is possible currently to hide a link by capitalizing a letter in the http protocol. This PR changes the regex to check for either case

Check List (Check all the applicable boxes)

• [x] My code follows the code style of this project.
• [ ] My change requires changes to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] All new and existing tests passed.
• [x] This PR does not contain plagiarized content.
• [x] The title of my pull request is a short description of the requested changes.