Update tutorial to mention tcrblosum usage

Author: felixpetschko

docs/tutorials/tutorial_3k_tcr.ipynb

@@ -1423,10 +1423,11 @@
     "\n",
     "To this end, we need to set `metric=\"tcrdist\"` and specify a `cutoff` parameter.\n",
     "The distance is based on the [BLOSUM62](https://en.wikipedia.org/wiki/BLOSUM) matrix.\n",
-    "For instance, a distance of `10` is equivalent to 2 Rs mutating into N.\n",
-    "This appoach was initially proposed by Dash et al. {cite}`TCRdist` and is based on the [tcrdist3](https://github.com/kmayerb/tcrdist3) implementation.\n",
+    "This approach was initially proposed by Dash et al. {cite}`TCRdist` and is based on the [tcrdist3](https://github.com/kmayerb/tcrdist3) implementation.\n",
+    "For instance, a distance of `12` is equivalent to two `R`s mutating into `K`s with the default parameters.\n",
+    "Alternatively, [TCRBLOSUM](https://doi.org/10.1093/bib/bbae602) alpha/beta substitution matrices can be selected with `base_matrix=\"tcrblosum\"`.\n",
     "\n",
-    "All cells with a distance between their CDR3 sequences lower than `cutoff` will be connected in the network.\n"
+    "Cells are connected in the network when their CDR3 sequence distances are at or below `cutoff`. In this case, this must hold for both receptor arms (`receptor_arms=\"all\"`, i.e. both VJ and VDJ chains), considering any possible dual immune receptor chain pairing (`dual_ir=\"any\"`).\n"
    ]
   },
   {
@@ -1464,6 +1465,7 @@
     "    metric=\"tcrdist\",\n",
     "    sequence=\"aa\",\n",
     "    cutoff=15,\n",
+    "    # base_matrix=\"tcrblosum\",\n",
     ")"
    ]
   },