Add helpful resources for learning Manim in the landing page.

Enhancement proposal

I suggested adding a channel in the discord server called #beginner-resources that would help beginners get started with Manim.

@behackl also suggested adding this type of information in the docs/ landing page.

I think this would be a good idea! We could probably add some of the resources we compiled from the ?sp tutorials snippet:

Most tutorials online are outdated, but here are some that aren't:
Try manim:
https://try.manim.community/
kolibril13's flying frames:
https://flyingframes.readthedocs.io/en/latest/
Brian Amadee's YouTube tutorials:
https://www.youtube.com/watch?v=MOv6yN7b2aI&list=PLWOlLjdyZm2NQD1YZmEPB0dwbd0yKINAT
Theorem of Beethoven's YouTube tutorials:
https://www.youtube.com/watch?v=mbjuZa5r-z4
Our documentation:
https://docs.manim.community/en/latest/tutorials.html

If there any other good resources out there, feel free to list them below 👍