DOC Add benchmarking cookbook (microsoft#1078)

Author: fdubut

doc/_toc.yml

@@ -6,6 +6,7 @@ chapters:
     - file: cookbooks/1_sending_prompts
     - file: cookbooks/2_precomputing_turns
     - file: cookbooks/3_copyright_violations
+    - file: cookbooks/4_benchmarking_models
   - file: setup/install_pyrit
     sections:
     - file: setup/jupyter_setup