Create GitHub actions

[fepegar]

Fixes:

• No more credits on Travis CI #711

Related to:

• Run Travis CI on different operating systems #429

Description
Migration from Travis CI to GitHub Actions.

Checklist

• I have read the CONTRIBUTING docs and have a developer setup (especially important are pre-commitand pytest)
• Non-breaking change (would not break existing functionality)
• Breaking change (would cause existing functionality to change)
• Tests added or modified to cover the changes
• Integration tests passed locally by running pytest
• In-line docstrings updated
• Documentation updated, tested running make html inside the docs/ folder
• This pull request is ready to be reviewed
• If the PR is ready and there are multiple commits, I have squashed them and force-pushed

[codecov]

Codecov Report

Merging #713 (9b93a5e) into master (f0c5a25) will decrease coverage by 0.38%.
The diff coverage is 78.43%.

@@            Coverage Diff             @@
##           master     #713      +/-   ##
==========================================
- Coverage   95.49%   95.10%   -0.39%     
==========================================
  Files          72       72              
  Lines        4348     4374      +26     
==========================================
+ Hits         4152     4160       +8     
- Misses        196      214      +18     

Impacted Files	Coverage Δ
torchio/data/image.py	89.71% <33.33%> (-0.32%)	⬇️
torchio/data/io.py	93.47% <60.86%> (-2.91%)	⬇️
torchio/__init__.py	100.00% <100.00%> (ø)
torchio/data/dataset.py	95.65% <100.00%> (+0.09%)	⬆️
torchio/transforms/augmentation/composition.py	91.02% <100.00%> (ø)
...ansforms/augmentation/intensity/random_ghosting.py	99.02% <100.00%> (ø)
...o/transforms/augmentation/spatial/random_affine.py	96.20% <100.00%> (+0.02%)	⬆️
torchio/transforms/preprocessing/spatial/resize.py	100.00% <100.00%> (ø)
torchio/transforms/transform.py	97.01% <100.00%> (+0.05%)	⬆️
torchio/visualization.py	93.95% <100.00%> (+0.08%)	⬆️
... and 1 more

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