implement frames save and open from ppi

src/app.cpp

@@ -54,7 +54,7 @@ void App::create()
 
 void App::open_document(std::string path)
 {
-    std::regex r(R"((.*)[\\/]?([^\\/]+)\.(\w+)$)");
+    std::regex r(R"((.*)[\\/]([^\\/]+)\.(\w+)$)");
     std::smatch m;
     if (!std::regex_search(path, m, r))
         return;