Update README and documentation landing page, improve way how 3b1b is credited (#4077)

* Update readme to properly credit Grant Sanderson and revise dismissive language

* Adjust readme and add landing-page mention about Grant's Manim

* Apply suggestions from code review

---------

Co-authored-by: Benjamin Hackl <[email protected]>

Author: czuzu

README.md

@@ -22,7 +22,7 @@
 Manim is an animation engine for explanatory math videos. It's used to create precise animations programmatically, as demonstrated in the videos of [3Blue1Brown](https://www.3blue1brown.com/).
 
 > [!NOTE]
-> This repository is maintained by the Manim Community and is not associated with Grant Sanderson or 3Blue1Brown in any way (although we are definitely indebted to him for providing his work to the world). If you would like to study how Grant makes his videos, head over to his repository ([3b1b/manim](https://github.com/3b1b/manim)). This fork is updated more frequently than his, and it's recommended to use this fork if you'd like to use Manim for your own projects.
+> The community edition of Manim has been forked from 3b1b/manim, a tool originally created and open-sourced by Grant Sanderson, also creator of the 3Blue1Brown educational math videos. While Grant Sanderson’s repository continues to be maintained separately by him, he is not among the maintainers of the community edition. We recommend this version for its continued development, improved features, enhanced documentation, and more active community-driven maintenance. If you would like to study how Grant makes his videos, head over to his repository ([3b1b/manim](https://github.com/3b1b/manim)).
 
 ## Table of Contents:
 

docs/source/index.rst

@@ -21,8 +21,9 @@ in the right place!
 
 .. note::
 
-   Please be aware that there are different, incompatible versions
-   of Manim available. Check our :ref:`installation FAQ <different-versions>`
+   Please be aware that there are different, incompatible versions of Manim available.
+   ManimCE was forked from 3b1b/manim, originally created and open-sourced by Grant Sanderson, creator of [3Blue1Brown](https://www.youtube.com/channel/UCYO_jab_esuFRV4b17AJtAw) educational math videos.
+   Check our :ref:`installation FAQ <different-versions>`
    to learn more!
 
 - The :doc:`Installation <installation>` section has the latest and