Properly apply aria-hidden on non HTMLElements (#4868)

svgs were still accessible by screenreaders durning DnD operations, this fixes that

Author: LFDanLu

packages/@react-aria/overlays/src/ariaHideOutside.ts

@@ -17,10 +17,6 @@ let observerStack = [];
 
 const supportsInert = typeof HTMLElement !== 'undefined' && Object.prototype.hasOwnProperty.call(HTMLElement.prototype, 'inert');
 
-interface InertElement extends HTMLElement {
-  inert: boolean
-}
-
 /**
  * Hides all elements in the DOM outside the given targets from screen readers using aria-hidden,
  * and returns a function to revert these changes. In addition, changes to the DOM are watched
@@ -87,14 +83,14 @@ export function ariaHideOutside(targets: Element[], root = document.body) {
 
     // If already aria-hidden, and the ref count is zero, then this element
     // was already hidden and there's nothing for us to do.
-    let alreadyHidden = supportsInert ? (node as InertElement).inert : node.getAttribute('aria-hidden') === 'true';
+    let alreadyHidden = supportsInert && node instanceof HTMLElement ? node.inert : node.getAttribute('aria-hidden') === 'true';
     if (alreadyHidden && refCount === 0) {
       return;
     }
 
     if (refCount === 0) {
-      supportsInert ?
-      ((node as InertElement).inert = true) :
+      supportsInert && node instanceof HTMLElement ?
+      node.inert = true :
       node.setAttribute('aria-hidden', 'true');
     }
 
@@ -159,8 +155,8 @@ export function ariaHideOutside(targets: Element[], root = document.body) {
     for (let node of hiddenNodes) {
       let count = refCountMap.get(node);
       if (count === 1) {
-        supportsInert ?
-        ((node as InertElement).inert = false) :
+        supportsInert && node instanceof HTMLElement ?
+        node.inert = false :
         node.removeAttribute('aria-hidden');
         refCountMap.delete(node);
       } else {