Link OpenFold repo from the docs

The intro part taken from the main README (which makes a title on GitHub) obviously did not link to itself but now the repo is hard to find when reading the (great!) docs :)

docs/source/index.md

@@ -5,7 +5,7 @@
 :align: center
 :alt: Comparison of OpenFold and AlphaFold2 predictions to the experimental structure of PDB 7KDX, chain B._
 ```
-Welcome to the Documentation for OpenFold, the fully open source, trainable, PyTorch-based reproduction of DeepMind's 
+Welcome to the Documentation for [OpenFold](https://github.com/aqlaboratory/openfold), the fully open source, trainable, PyTorch-based reproduction of DeepMind's 
 [AlphaFold 2](https://github.com/deepmind/alphafold).
 
 Here, you will find guides and documentation for:
@@ -115,4 +115,4 @@ Aux_seq_files.md
 OpenFold_Parameters.md
 FAQ.md
 original_readme.md
-```
+```