Fix relative link handling in Element Desktop (#7708)

Author: t3chguy

src/linkify-matrix.ts

@@ -132,9 +132,9 @@ const escapeRegExp = function(string): string {
 };
 
 // Recognise URLs from both our local and official Element deployments.
-// Anyone else really should be using matrix.to.
+// Anyone else really should be using matrix.to. vector:// allowed to support Element Desktop relative links.
 export const ELEMENT_URL_PATTERN =
-    "^(?:https?://)?(?:" +
+    "^(?:vector://|https?://)?(?:" +
         escapeRegExp(window.location.host + window.location.pathname) + "|" +
         "(?:www\\.)?(?:riot|vector)\\.im/(?:app|beta|staging|develop)/|" +
         "(?:app|beta|staging|develop)\\.element\\.io/" +

src/utils/permalinks/Permalinks.ts

@@ -362,7 +362,11 @@ export function tryTransformEntityToPermalink(entity: string): string {
  * @returns {string} The transformed permalink or original URL if unable.
  */
 export function tryTransformPermalinkToLocalHref(permalink: string): string {
-    if (!permalink.startsWith("http:") && !permalink.startsWith("https:") && !permalink.startsWith("matrix:")) {
+    if (!permalink.startsWith("http:") &&
+        !permalink.startsWith("https:") &&
+        !permalink.startsWith("matrix:") &&
+        !permalink.startsWith("vector:") // Element Desktop
+    ) {
         return permalink;
     }