Support code highlighting (#1577)

.github/workflows/build.yml

@@ -17,7 +17,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install -U pip
-          python -m pip install -U docutils
+          python -m pip install -r requirements.txt
 
       - name: Build
         run: |

requirements.txt

@@ -1,6 +1,7 @@
 # Requirements for building PEPs with Sphinx
-sphinx >= 3.5
-docutils >= 0.16
+Pygments >= 2.9.0
+Sphinx >= 4.0.2
+docutils >= 0.17.1
 
 # For RSS
 feedgen >= 0.9.0  # For RSS feed