Add missing docs for v19.23 (#2495)

* Add missing docs for v19.23

* remove duplicate yolo entry

* fix link of loss_yolo_ in term_index

docs/docs/ml.xml

@@ -353,6 +353,10 @@ Davis E. King. <a href="http://jmlr.csail.mit.edu/papers/volume10/king09a/king09
                   <name>loss_multibinary_log</name>
                   <link>dlib/dnn/loss_abstract.h.html#loss_multibinary_log_</link>
                </item>
+               <item>
+                  <name>loss_barlow_twins</name>
+                  <link>dlib/dnn/loss_abstract.h.html#loss_barlow_twins_</link>
+               </item>
             </sub>
          </item>
          <item nolink="true">

docs/docs/term_index.xml

@@ -147,6 +147,9 @@
          <term file="ml.html" name="loss_mean_squared_multioutput_" include="dlib/dnn.h"/>
          <term file="ml.html" name="loss_mmod_" include="dlib/dnn.h"/>
          <term file="dlib/dnn/loss_abstract.h.html" name="mmod_options" include="dlib/dnn.h"/>
+         <term file="ml.html" name="loss_yolo_" include="dlib/dnn.h"/>
+         <term file="dlib/dnn/loss_abstract.h.html" name="yolo_options" include="dlib/dnn.h"/>
+         <term file="dlib/dnn/loss_abstract.h.html" name="loss_barlow_twins_" include="dlib/dnn.h"/>
 
          <term file="dlib/dnn/solvers_abstract.h.html" name="EXAMPLE_SOLVER" include="dlib/dnn.h"/>
          <term file="dlib/dnn/solvers_abstract.h.html" name="sgd" include="dlib/dnn.h"/>