More cellxgene Galaxy information for the extensions (#2024)

This PR adds some more text and direct links to the cellxgene Galaxy section.

Thanks!


#### Reviewers
**Functional:** 

**Readability:** 

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## Changes
- add
- remove
- modify

docs/_site/posts/extensions.html

@@ -125,8 +125,12 @@ <h4 id="cellxgene-vip-visualization-in-plugin">cellxgene-VIP (Visualization in P
 
 <h4 id="galaxy">Galaxy</h4>
 
-<p><a href="https://singlecell.usegalaxy.eu/">Galaxy</a> is an open source, web-based platform for data intensive biomedical research. cellxgene can be accessed within Galaxy to view analyzed datasets. 
-See also the relevant <a href="https://www.biorxiv.org/content/10.1101/2020.06.06.137570v1.full.pdf">publication</a></p>
+<p><a href="https://galaxyproject.org">Galaxy</a> is an open source, collaborative, web-based platform for data intensive biomedical research.
+Galaxy provides various tools for <a href="https://singlecell.usegalaxy.eu/">single-cell data analysis</a> and also infrastructure to the
+<a href="https://humancellatlas.usegalaxy.eu">Galaxy Human Cell Atlas project</a>. cellxgene can be <a href="https://usegalaxy.eu/root?tool_id=interactive_tool_cellxgene">
+  accessed within Galaxy</a> to view analyzed datasets. See also the relevant <a href="https://doi.org/10.1093/gigascience/giaa102">publication</a>
+
+</p>
 
 <h4 id="single-cell-portal">Single Cell Portal</h4>