Setting for disabling /mentions tab highlight (#1994)

Co-authored-by: pajlada <rasmus.karlsson@pajlada.com>

src/widgets/settingspages/GeneralPage.cpp

@@ -625,6 +625,8 @@ void GeneralPage::initLayout(GeneralPageView &layout)
     layout.addCheckbox("Combine multiple bit tips into one", s.stackBits);
     layout.addCheckbox("Ask for confirmation when uploading an image",
                        s.askOnImageUpload);
+    layout.addCheckbox("Messages in /mentions highlights tab",
+                       s.highlightMentions);
 
     layout.addStretch();