Implement FLAG_WINDOW_RESIZABLE for web

Fixes raysan5#3231

src/rcore.c

@@ -914,9 +914,9 @@ void InitWindow(int width, int height, const char *title)
     // Check fullscreen change events(note this is done on the window since most browsers don't support this on #canvas)
     //emscripten_set_fullscreenchange_callback(EMSCRIPTEN_EVENT_TARGET_WINDOW, NULL, 1, EmscriptenResizeCallback);
     // Check Resize event (note this is done on the window since most browsers don't support this on #canvas)
-    //emscripten_set_resize_callback(EMSCRIPTEN_EVENT_TARGET_WINDOW, NULL, 1, EmscriptenResizeCallback);
+    emscripten_set_resize_callback(EMSCRIPTEN_EVENT_TARGET_WINDOW, NULL, 1, EmscriptenResizeCallback);
     // Trigger this once to get initial window sizing
-    //EmscriptenResizeCallback(EMSCRIPTEN_EVENT_RESIZE, NULL, NULL);
+    EmscriptenResizeCallback(EMSCRIPTEN_EVENT_RESIZE, NULL, NULL);
 
     // Support keyboard events -> Not used, GLFW.JS takes care of that
     //emscripten_set_keypress_callback("#canvas", NULL, 1, EmscriptenKeyboardCallback);
@@ -6165,8 +6165,8 @@ static EM_BOOL EmscriptenWindowResizedCallback(int eventType, const EmscriptenUi
     return 1;   // The event was consumed by the callback handler
 }
 
-EM_JS(int, GetCanvasWidth, (), { return canvas.clientWidth; });
-EM_JS(int, GetCanvasHeight, (), { return canvas.clientHeight; });
+EM_JS(int, GetWindowInnerWidth, (), { return window.innerWidth; });
+EM_JS(int, GetWindowInnerHeight, (), { return window.innerHeight; });
 
 // Register DOM element resize event
 static EM_BOOL EmscriptenResizeCallback(int eventType, const EmscriptenUiEvent *event, void *userData)
@@ -6176,8 +6176,8 @@ static EM_BOOL EmscriptenResizeCallback(int eventType, const EmscriptenUiEvent *
 
     // This event is called whenever the window changes sizes,
     // so the size of the canvas object is explicitly retrieved below
-    int width = GetCanvasWidth();
-    int height = GetCanvasHeight();
+    int width = GetWindowInnerWidth();
+    int height = GetWindowInnerHeight();
     emscripten_set_canvas_element_size("#canvas",width,height);
 
     SetupViewport(width, height);    // Reset viewport and projection matrix for new size