Added ability to supply JSON from standard input

sdl_helpers.h

@@ -90,6 +90,12 @@ SDL_Rect surface_align(const SDL_Surface* base, const SDL_Surface* applied,
 // log - output errors to this ostream, silent if NULL
 bool read_config_json(nlohmann::json& cfg, const std::string& filename, std::ostream* log = &std::cout);
 
+// Reads the stream and tries to parse JSON from it with comments
+// cfg - output json struct
+// in - input stream to read
+// log - output errors to this ostream, silent if NULL
+bool read_config_json(nlohmann::json& cfg, std::istream& in, std::ostream* log = &std::cout);
+
 // JSON Extractors - They do not override already set values if key is not present
 
 void json_extract(const nlohmann::json& j, const std::string& key, std::string& out);