[refactor] add namespace 'crossdesk' to codebase

src/screen_capturer/macosx/screen_capturer_sck_impl.mm

@@ -22,6 +22,8 @@
 #include "display_info.h"
 #include "rd_log.h"
 
+namespace crossdesk {
+
 static const int kFullDesktopScreenId = -1;
 class ScreenCapturerSckImpl;
 
@@ -485,4 +487,5 @@ std::unique_ptr<ScreenCapturer> ScreenCapturerSck::CreateScreenCapturerSck() {
   _capturer = nullptr;
 }
 
-@end
+@end
+}  // namespace crossdesk