add javascript binding and file picker for web

src/app_events.cpp

@@ -15,8 +15,10 @@ void win32_show_cursor(bool visible);
 bool win32_clipboard_set_text(const std::string & s);
 std::string win32_clipboard_get_text();
 #elif __APPLE__
-#else
+#elif __LINUX__
 #include <tinyfiledialogs.h>
+#elif __WEB__
+void webgl_pick_file(std::function<void(std::string)> callback);
 #endif
 
 
@@ -149,6 +151,11 @@ void App::pick_image(std::function<void(std::string path)> callback)
     std::string path = win32_open_file("Image Files (*.jpg, *.png)\0*.jpg;*.png");
     if (!path.empty())
         callback(path);
+#elif __LINUX__
+    if (auto p = tinyfd_openFileDialog("Open File", "", 0, nullptr, nullptr, false))
+        callback(p);
+#elif __WEB__
+    webgl_pick_file(callback);
 #endif
 }
 
@@ -196,6 +203,8 @@ void App::pick_file(std::vector<std::string> types, std::function<void (std::str
 #elif __LINUX__
     if (auto p = tinyfd_openFileDialog("Open File", "", 0, nullptr, nullptr, false))
         callback(p);
+#elif __WEB__
+    webgl_pick_file(callback);
 #endif
 }