feat: add IGN router

[LBasara]

No description provided.

[LBasara]

The commit should fix #148 , adding IGN Geoservices directions and isochrones.

[mthh]

Thank you! I'll start reviewing it very soon, hoping to merge it within the week if all goes well!

[mthh]

For now, CI jobs are failing because the poetry.lock file is no longer synchronized with the pyproject.toml file.

Once you have seen my previous comment (about the need to write the poetry dependency on the one hand, and about the dependencies on responses on the other), could you push an updated version of this poetry.lock file?

[mthh]

Thanks for the pyproject/poetry changes!
I left a few additional comments before merging.

In addition, you should add an entry in the documentation, in the docs/index.rst file (between HereMaps and MapboxOSRM).

IGN
---

.. autoclass:: routingpy.routers.IGN
   :members:

   .. automethod:: __init__

[mthh]

If you're OK with that, I'll push the few changes I suggested to your branch so I can merge it within the week!

Edit: I also changed the name of the PR for better visibility.

[LBasara]

If you're OK with that, I'll push the few changes I suggested to your branch so I can merge it within the week!

Edit: I also changed the name of the PR for better visibility.

Sorry I didn't have much bandwidth in the previous weeks to address the changes.
I have time now if I can help, otherwise I'm perfectly fine with the changes, and if you can merge them it would be awesome.

[mthh]

Sorry I didn't have much bandwidth in the previous weeks to address the changes.

No problem, you did most of the work, and the last few things I asked for were minor details!

I'll let it sit for another half-day, but overall I think I'm now OK with merging it.