add hackr.io to everything in one place category

[paulaxisabel]

Summary of your changes

Description

I have added hackr.io to Everything at one place category. Hackr.io is a valuable resource for anyone who wants to learn new tech skills. It provides a curated list of the best online courses and tutorials, so you can be sure that you are learning from the best. Hackr.io also evaluates each course and tutorial, so you can be confident that you are getting a quality education.

Checklist

• [x] My change follows the Contributing Guidelines
• [x] I have added only one new link to the list.
• [x] I have checked that the link that I added does NOT exist in the project already.
• [x] I have sorted the link alphabetically under the related section.