Set the mention and error color according to colorscheme

Use kirigami to set the proper link and error color for mentions and error underlining in chatbox

This is with my own colorscheme:

![image](/uploads/6269b85f936a98b02f42a9ce01da76b1/image.png)

src/qml/Component/ChatBox/ChatBar.qml

@@ -394,6 +394,8 @@ QQC2.Control {
         cursorPosition: textField.cursorPosition
         selectionStart: textField.selectionStart
         selectionEnd: textField.selectionEnd
+        mentionColor: Kirigami.Theme.linkColor
+        errorColor: Kirigami.Theme.negativeTextColor
         Component.onCompleted: {
             RoomManager.chatDocumentHandler = documentHandler;
         }