I'm using `gganimate` to create some .gif files that I want to insert into my reports. I'm able to save the files and view them fine, however, I find that the displayed size is small: 480x480. Is there a way to adjust that - perhaps along the lines of `height` and `width` arguments in `ggsave()`? 

I can zoom in but that impacts the quality poorly and makes it rather unreadable for my use case.

Here's some sample code: 

```
gplot <- 
  ggplot(gapminder, 
         aes(x = gdpPercap, y = lifeExp, colour = continent, 
             size = pop, 
             frame = year)) +
    geom_point(alpha = 0.6) + 
    scale_x_log10()

gganimate(gplot, "test.gif")

```

Below is the output for this code.

[![test.gif](https://i.stack.imgur.com/j13q5.gif)](https://i.stack.imgur.com/j13q5.gif)