Tinkering with input

I want to move keyboard input defs to the Python API. I laid the groundwork for it today.

From the JANKFILE:

- working on API endpoint `_registerInputAction`.

it will add "_py" as a suffix to the action string and register it along with other scene actions.

- Adding public Scene methods. These are on the base class with default of return `false`.

`bool Scene::registerActionInjected(int code, std::string name)` and `unregisterActionInjected`

the PythonScene (and other scenes that support injected user input) can override this method, check existing registrations, and return `true` when succeeding.

Also, upgraded to C++20 (g++ `c++2a`), mostly because I want to use map::contains.

src/Scene.cpp

@@ -23,3 +23,13 @@ std::string Scene::action(int code)
 {
     return actions[code];
 }
+
+bool Scene::registerActionInjected(int code, std::string name)
+{
+    return false;
+}
+
+bool Scene::unregisterActionInjected(int code, std::string name)
+{
+    return false;
+}