Enable exercise_style solution_follow_exercise feature

Author: mmcky

lectures/_config.yml

@@ -118,6 +118,8 @@ sphinx:
           "gG": "\\mathcal{G}"
           "hH": "\\mathcal{H}"
     mathjax_path: https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js
+    # sphinx-exercise
+    exercise_style: "solution_follow_exercise"
     rediraffe_redirects:
       index_toc.md: intro.md
     tojupyter_static_file_path: ["source/_static", "_static"]