Remove the numerical prefix from the file name and Fix links

[jaguarfi]

Description

In order to fix some of the broken links, the numerical prefix was removed from the file name. This change will help to add new chapters and to avoid renaming all the links that would be affected by having to change the numerical prefix in the file names. This commit also fixes some links that hard-coded the domain to localhost:8000 and some other links that were broken.

Fixes: #23

Testing

I used the search function of VSCode to find the links, and I fixed the references one by one while I navigated the course in the localhost. I basically tested all the links manually.

Is it Done?

Clean up your git commit history before submitting the pull request!

• [ ] I (developer) have created unit tests and the tests pass
• [ ] I (developer) have created functional tests (Selenium tests) if applicable
• [X] I (developer) have tested the changes manually
• [ ] Reviewer has finished the code review
• [ ] After the review, the developer has made changes accordingly
• [ ] Customer/Teacher has accepted the implementation of the feature

[jaguarfi]

You can merge this one first. I will resolve any merging conflict in the other PRs