fix: typo in presentation site

frontend/static/index.html

@@ -142,7 +142,7 @@ <h4>What is it?</h4>
                   <li>Which indicators will you use?</li>
                   <li>
                     Do you have access to data-sources that will enable you to measure them? How
-                    often? With which level of detail?
+                    often? At which level of detail?
                   </li>
                   <li>Once you start measuring them, which figures do you expect to find?</li>
                   <li>