Add "full frontal" render perspecetive

[alerque]

The angle used for render shots is great sometimes and terrible others.

1. Consider making the camera angle configurable.
2. Add a "full frontal" rendered shot. Most useful perhaps for hardback (c.f. Add hard cover binding support #5) and perhaps with a little bit of skewedness, but this is cool:
   https://mobile.twitter.com/19cWT/status/1511718712092598273