Update doc-sitemap-external.md

Added additional spacing to tags in the first drop-down

docs/doc-sitemap-external.md

@@ -42,7 +42,9 @@ Tools to get data without going to the Portal:
           <li><a href="https://github.com/hubmapconsortium/hubmap-data-exploration-workshop/blob/main/HuBMAP_Gene_Ontology_Enrichment_Analysis_(GOEA)_with_goatools_HBM538_PHSC_677.ipynb">Venn Diagrams for Comparing Marker Genes </a>: Generate Venn & Super Venn Diagrams to compare marker genes.</li>
           <li><a href="https://github.com/hubmapconsortium/hubmap-data-exploration-workshop/blob/main/HuBMAP_String_Database_protein_protein_interaction_networks_version_03_HBM538_PHSC_677.ipynb">Protein-Protein Interaction Networks</a>: Generate these networks from a list of marker genes with Python's stringdb library.</li>
           <li><a href="https://github.com/hubmapconsortium/hubmap-data-exploration-workshop/blob/main/HuBMAP_Gene_Ontology_Enrichment_Analysis_(GOEA)_with_goatools_HBM538_PHSC_677.ipynb">Gene Ontology Enrichment Analysis</a>: Use the Python goatools library for gene ontology enrichment analysis.</li>
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   - <a href="https://hubmapconsortium.org/featured-publications/">HuBMAP Publications</a>: See more than 330 featured publications to learn how HuBMAP tools and data are advancing discovery.