Add GitHub Actions, remove travis

[jason-fox]

Proposed changes

As I'm sure you are aware from the TSC minutes, it appears that Travis is transitioning towards a paid pricing model. It would be opportune for active FOSS Projects to migrate to use the integrated GitHub Actions. It looks like each GitHub account is safe until January, but then travis-ci.org goes read-only then the 100000 credits start counting down. There is no clarity over if/how to obtain more credits, and indeed if they can be obtained in a timely manner.

Types of changes

What types of changes does your code introduce to the project: Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of
them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before
merging your code.

• I have read the CONTRIBUTING doc
• I have signed the CLA
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you
did and what alternatives you considered, etc...

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️

[jason-fox]

I have read the CLA Document and I hereby sign the CLA

[jason-fox]

recheckcla

[jason-fox]

Test run can be seen here: https://github.com/jason-fox/fiware-pep-proxy/actions/runs/391528886