Import zip via drag and drop in project manager.

Dropping a single ZIP file in the project manager will now prompt the
import dialog.

editor/project_manager.cpp

@@ -2281,6 +2281,11 @@ void ProjectManager::_install_project(const String &p_zip_path, const String &p_
 }
 
 void ProjectManager::_files_dropped(PackedStringArray p_files, int p_screen) {
+	if (p_files.size() == 1 && p_files[0].ends_with(".zip")) {
+		const String file = p_files[0].get_file();
+		_install_project(p_files[0], file.substr(0, file.length() - 4).capitalize());
+		return;
+	}
 	Set<String> folders_set;
 	DirAccess *da = DirAccess::create(DirAccess::ACCESS_FILESYSTEM);
 	for (int i = 0; i < p_files.size(); i++) {