Add tutorial links to main README.md

Summary: <See title>

Reviewed By: bottler

Differential Revision: D41534604

fbshipit-source-id: 20111db87083b2cce7374cc2bd223ae220d7b010

Author: davnov134

.github/implicitron_config.gif

@@ -56,6 +56,11 @@ Get started with PyTorch3D by trying one of the tutorial notebooks.
 |:------------------------------------------------------------:|:--------------------------------------------------:|
 | [Fit Textured Volume](https://github.com/facebookresearch/pytorch3d/blob/main/docs/tutorials/fit_textured_volume.ipynb)| [Fit A Simple Neural Radiance Field](https://github.com/facebookresearch/pytorch3d/blob/main/docs/tutorials/fit_simple_neural_radiance_field.ipynb)|
 
+| <img src="https://raw.githubusercontent.com/facebookresearch/pytorch3d/main/.github/fit_textured_volume.gif" width="310"/> | <img src="https://raw.githubusercontent.com/facebookresearch/pytorch3d/main/.github/implicitron_config.gif" width="310" height="310"/>
+|:------------------------------------------------------------:|:--------------------------------------------------:|
+| [Fit Textured Volume in Implicitron](https://github.com/facebookresearch/pytorch3d/blob/main/docs/tutorials/implicitron_volumes.ipynb)| [Implicitron Config System](https://github.com/facebookresearch/pytorch3d/blob/main/docs/tutorials/implicitron_config_system.ipynb)|
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