[WIP] Documentation, Test cases and CI for trx_file_memmap

[ValHayot]

• Extended docstrings for trx_file_memmap.py
• Added type annotations to trx_file_memmap.py
• Added test cases [WIP]
• Created a GitHub workflow for CI

[frheault]

I went through the code and everything looks great.
I tested it with my example code/data and play around a little in a console.
I was just trying to make sure memory and/or hard drive were freed up at the right moment.

And I ran the test, everything seems to be working as intended!

Is it possible to add a requirements.txt with dipy, numpy==1.21 and pytest?
(Maybe writing somewhere this only works in python3.9?

[arokem]

I added a setup.cfg file in ValHayot#1.

I also added a license file. @frheault : are you OK with BSD 2-clause?

[frheault]

I just realized a small error:
In deepcopy there is a conversion in case the user assigns an affine as numpy array and convert it to a list for the json file.
BUT if the affine (and dimensions) are already lists it crashes, a check should be done with isinstance first.

tmp_header["VOXEL_TO_RASMM"] = tmp_header["VOXEL_TO_RASMM"].tolist()
tmp_header["DIMENSIONS"] = tmp_header["DIMENSIONS"].tolist()