Clip commonly seen labels used for display names to prevent Unicode spam

Unfortunately a pretty common spam/annoyance online is putting "spam"
via abusing Unicode symbols - which is used for multilingual support -
in display names. This typically results in an unreadable word jumble in
our UI, which looks bad.

So I decided to put a stop to that by clipping some labels that could be
used for this crap. I didn't cover *everything* yet, but this at least
prevents these idiots from showing up in the completion menu, the room
member list and as authors for messages.

src/chatbar/CompletionMenu.qml

@@ -92,6 +92,7 @@ QQC2.Popup {
                         Delegates.SubtitleContentItem {
                             itemDelegate: completionDelegate
                             labelItem.textFormat: Text.PlainText
+                            labelItem.clip: true // Intentional to limit insane Unicode in display names
                             subtitle: completionDelegate.subtitle ?? ""
                             subtitleItem.textFormat: Text.PlainText
                         }