Add invidious instance EduVid Tubus

[magicbrothers]

• I carefully read the contribution guidelines and agree to them.
• I have tested the API against NewPipe.
• I agree to create a pull request for NewPipe as soon as possible to make it compatible with the changed API.

As this is a trivial change, I didn't test it. Also, my very old laptop (32bit, 512MB RAM) probably isn't suited for Android development.

Please, as you already have all the required tools installed and a development environment set up, test it yourself, that would be kind :)

[FireMasterK]

Why isn't this instance on https://github.com/iv-org/documentation/blob/master/Invidious-Instances.md? (the public instances list)

[magicbrothers]

As stated here, EduVid Tubus isn't "just another" Invidious instance, but primarily for use in education.
More information can be found in this blog post (German)