Added x-attach-split-to-window command line arg (#2411)

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

src/common/Args.hpp

@@ -15,7 +15,13 @@ public:
     bool printVersion{};
     bool crashRecovery{};
     bool shouldRunBrowserExtensionHost{};
+    // Shows a single chat. Used on windows to embed in another application.
+    bool isFramelessEmbed{};
+    boost::optional<unsigned long long> parentWindowId{};
+
+    // Not settings directly
     bool dontSaveSettings{};
+    bool dontLoadMainWindow{};
     boost::optional<WindowLayout> customChannelLayout;
     bool verbose{};