Allow show sender detail from message context menu

When curtain user is spamming a lot of messages in a short amount
of time, mod need to scroll all the way up to the first spam message to
know who send those spam message, thus start banning them.

This patch add a context menu to open the sender detail dialog, it could
make banning the spam user and batch-deleting spam messages easier.

src/qml/MessageDelegateContextMenu.qml

@@ -67,6 +67,13 @@ DelegateContextMenu {
             onTriggered: Clipboard.saveText(root.selectedText.length > 0 ? root.selectedText : root.plainText)
         },
         DelegateContextMenu.ReportMessageAction {},
+        Kirigami.Action {
+            text: i18nc("@action:inmenu", "Show User")
+            icon.name: "username-copy"
+            onTriggered: {
+                RoomManager.resolveResource(author.id)
+            }
+        },
         DelegateContextMenu.ViewSourceAction {},
         Kirigami.Action {
             text: i18n("Copy Link")