[rcore] [web] Updates SetWindowState() and ClearWindowState() to handle FLAG_WINDOW_MAXIMIZED for PLATFORM_WEB

[asdqwe]

Complementary to #4397. This PR can be tested with:

// Note: usage of `minshell.html` is recommended since it won't force canvas CSS overrides

#include "raylib.h"
int main(void) {
    InitWindow(800, 450, "test");
    SetTargetFPS(60);

    SetWindowState(FLAG_WINDOW_RESIZABLE);

    while (!WindowShouldClose()) {

        if (IsKeyPressed(KEY_ONE)) SetWindowState(FLAG_WINDOW_MAXIMIZED);
        if (IsKeyPressed(KEY_TWO)) ClearWindowState(FLAG_WINDOW_MAXIMIZED);

        if (IsKeyPressed(KEY_Q)) MaximizeWindow();
        if (IsKeyPressed(KEY_W)) RestoreWindow();

        BeginDrawing();
        ClearBackground(RAYWHITE);
        DrawText("test", 20, 20, 20, BLACK);
        EndDrawing();
    }
    CloseWindow();
    return 0;
}

[raysan5]

@asdqwe Thanks for the further review!