combinatorial_embedding_to_pos, specify outer face

[ChristopheVuillot]

This PR adds the ability for the user to specify the triangulation and outer face when computing positions of the nodes for drawing.

The solution is the one discussed in #4699 (comment)

[dschult]

This look great! But still will need some basic tests before merging.
Can you look at the module (relative to the algorithms directory): tests/test_planar_drawing.py?
It uses pytest and is hopefully sufficiently readable that you could add a test to make sure
the new function works with a correct input...
Probably good to also check that it gives a reasonable error if the input is not appropriate -- though I haven't thought about that for tis problem -- it might not make sense to do that...

Thank you

[ChristopheVuillot]

Thanks for the feedback, I will have a look about adding tests.