Ensure dependency installed

Ref: https://github.com/ai-robots-txt/ai.robots.txt/issues/60#issuecomment-2571437913
Ref: https://stackoverflow.com/questions/11783875/importerror-no-module-named-bs4-beautifulsoup

.github/workflows/main.yml

@@ -20,6 +20,7 @@ jobs:
         with:
           fetch-depth: 2
       - run: |
+          pip install beautifulsoup4
           git config --global user.name "ai.robots.txt"
           git config --global user.email "ai.robots.txt@users.noreply.github.com"
           git log -1