Request: implement lv_style_get_prop

[cydergoth]

lv_style_value_t v;
lv_res_t res = lv_style_get_prop(&style, LV_STYLE_BG_COLOR, &v);
if(res == LV_RES_OK) {  /*Found*/
    do_something(v.color);
}

From : https://docs.lvgl.io/master/overview/style.html

[nia-e]

WIll get to this tomorrow, the animation stuff is turning out to be a massive pain. But thanks!