Add Dockerfiles for development on CPU and GPU

[liam-adams]

Motivation and Context

This is for issue #19

How has this been tested?

I ran make test, make package and installed causalnex from source inside both of the docker containers. All tests passed and I ran the tutorial https://causalnex.readthedocs.io/en/latest/03_tutorial/01_first_tutorial.html on the created pip package

In the gpu image I ran into the same issue described here #138

Checklist

• [y] Read the contributing guidelines
• [n/a] Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• [y] Updated the documentation to reflect the code changes
• [n] Added a description of this change and added my name to the list of supporting contributions in the RELEASE.md file
• [n/a] Added tests to cover my changes
• [y] Assigned myself to the PR

Notice

• I acknowledge and agree that, by checking this box and clicking "Submit Pull Request":

• I submit this contribution under the Apache 2.0 license and represent that I am entitled to do so on behalf of myself, my employer, or relevant third parties, as applicable.

• I certify that (a) this contribution is my original creation and / or (b) to the extent it is not my original creation, I am authorised to submit this contribution on behalf of the original creator(s) or their licensees.

• I certify that the use of this contribution as authorised by the Apache 2.0 license does not violate the intellectual property rights of anyone else.

[GabrielAzevedoFerreiraQB]

This will be a great addition! thanks for putting the effort into it
I'd just to clarify a few things first

[GabrielAzevedoFerreiraQB]

It is good to merge! I wonder if you can just add a release note when you can, please?

[oentaryorj]

Removed scikit-learn from test_requirements and fixed linting. LGTM now