EA: add support for Zensical (#662)

<img width="1606" height="977" alt="Screenshot_2025-12-09_19-01-40"
src="https://github.com/user-attachments/assets/d0d4eb0c-81f7-4476-81ef-5cffa6341178"
/>


<img width="1801" height="1011" alt="Screenshot_2025-12-09_19-02-02"
src="https://github.com/user-attachments/assets/1de16ffd-315e-4a4b-a6d7-21bf4934c3fa"
/>

Author: humitos

src/ethicalads.js

@@ -251,6 +251,21 @@ export class EthicalAdsAddon extends AddonBase {
           this.setFixedFooterAdProperties(placement);
           knownPlacementFound = true;
         }
+      } else if (docTool.isZensical()) {
+        selector = "div.md-sidebar__scrollwrap";
+        element = document.querySelector(selector);
+
+        if (this.elementAboveTheFold(element)) {
+          placement.classList.add("ethical-alabaster");
+
+          placement.setAttribute("data-ea-type", "readthedocs-sidebar");
+          placement.setAttribute("data-ea-style", "image");
+          knownPlacementFound = true;
+        } else {
+          fixedFooterAdSelectors = ["div.md-footer-meta"];
+          this.setFixedFooterAdProperties(placement);
+          knownPlacementFound = true;
+        }
       }
 
       if (selector && knownPlacementFound) {