rustdoc: avoid drag gesture on right click

Author: notriddle

src/librustdoc/html/static/js/main.js

@@ -1286,7 +1286,10 @@ href="https://doc.rust-lang.org/${channel}/rustdoc/how-to-read-rustdoc.html\
         window.removeEventListener("mouseup", stopResize, false);
         removeClass(document.documentElement, "sidebar-resizing");
     };
-    const initResize = () => {
+    const initResize = e => {
+        if (e.altKey || e.ctrlKey || e.metaKey || e.button !== 0) {
+            return;
+        }
         window.addEventListener("mousemove", resize, false);
         window.addEventListener("mouseup", stopResize, false);
         addClass(resizer, "active");