Add support for opening links in incognito mode on Linux & BSD (#4745)

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

tests/src/XDGDesktopFile.cpp

@@ -0,0 +1,19 @@
+#include "util/XDGDesktopFile.hpp"
+
+#include <gtest/gtest.h>
+#include <QDebug>
+
+using namespace chatterino;
+
+TEST(XDGDesktopFile, String)
+{
+    auto desktopFile = XDGDesktopFile(":/001-mimeapps.list");
+    auto entries = desktopFile.getEntries("Default Applications");
+
+    ASSERT_EQ(entries["thisshould"], "");
+
+    ASSERT_EQ(entries["lol"], "");
+    ASSERT_EQ(entries["x-scheme-handler/http"], QString("firefox.desktop"));
+
+    ASSERT_EQ(desktopFile.getEntries("test").size(), 2);
+}