Add iqtree model used field to augur workflow documentation

docs/workflows/phylogenetic_construction/augur.md

@@ -290,6 +290,7 @@ The Nextstrain team hosts documentation surrounding the Augur workflow → Auspi
 | auspice_input_json | File | JSON file used as input to Auspice |
 | combined_assemblies | File | Concatenated FASTA file containing all samples |
 | distance_tree | File | The distance tree created in Newick (.nwk) format |
+| iqtree_model_used | String | The iqtree model used during augur tree |
 | keep_list | File | A list of samples included in the phylogenetic tree |
 | metadata_merged | File | Tab-delimited text file of the merged augur_metadata input files from all samples |
 | snp_matrix | File | The SNP distance matrix for all samples used in the phylogenetic tree |