Add more generic wanring message for source files

Author: liamjberrisford

.github/workflows/accessibility.yml

@@ -117,7 +117,7 @@ jobs:
               echo '```' >> pa11y_output.md
 
               base=$(basename "$file" .html)
-              echo "_⚠️ This issue likely originates from \`${base}.md\` or \`${base}.ipynb\`, which is used to generate this HTML file._" >> pa11y_output.md
+              echo "_⚠️ This issue likely originates from the source file (e.g., \`filename.md\`, \`filename.ipynb\`) used to generate this HTML output._" >> pa11y_output.md
               echo "" >> pa11y_output.md
             done
           fi