Add GitHub actions and replace Travis

[kplatis]

This pull request introduces 2 Github Actions that replace the existing Travis configuration:

1. test.yml that runs the unit tests and uploads the results. It runs when a change is pushed in any branch.
2. publish.yml that builds the tarball and publishes the package in PyPI. The PyPI token is already set . It runs when a new tag is pushed.

[kplatis]

@MFSY Should I also remove the already existing Travis configuration?

[kplatis]

@MFSY According to this post, there is no way to trigger tests when a pull request is merged. The only thing we can do is to restrict the branches in which the tests will run when pushed (merged)

[MFSY]

Hi @kplatis ,

I see. I think running the tests on the PR itself and restricting who can merge is okay.

[codecov-commenter]

Codecov Report

Merging #214 (a178bbd) into master (fe0bc90) will decrease coverage by 0.29%. The diff coverage is 96.87%.

@@            Coverage Diff             @@
##           master     #214      +/-   ##
==========================================
- Coverage   72.24%   71.95%   -0.30%     
==========================================
  Files          79       79              
  Lines        4886     4817      -69     
==========================================
- Hits         3530     3466      -64     
+ Misses       1356     1351       -5     

Impacted Files	Coverage Δ
kgforge/core/forge.py	70.05% <94.44%> (+4.71%)	:arrow_up:
tests/core/test_forge.py	100.00% <100.00%> (ø)
tests/core/conversions/conftest.py	72.22% <0.00%> (-3.59%)	:arrow_down:
...sts/specializations/stores/test_bluebrain_nexus.py	91.59% <0.00%> (-0.72%)	:arrow_down:
kgforge/core/commons/execution.py	67.39% <0.00%> (-0.36%)	:arrow_down:
tests/conftest.py	98.07% <0.00%> (-0.32%)	:arrow_down:
kgforge/core/archetypes/store.py	61.36% <0.00%> (-0.22%)	:arrow_down:
tests/core/test_resource.py	100.00% <0.00%> (ø)
tests/core/conversions/test_rdf.py	100.00% <0.00%> (ø)
tests/core/wrappings/test_paths.py	100.00% <0.00%> (ø)
... and 7 more

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