Add Github actions

[muffix]

Description

Adds a Github actions pipeline that builds the binaries, runs all tests and checks. This can eventually replace Travis or some parts that are run in its pipeline.

Also adds a check that all source files have been formatted with goimports. This explains the reordering of imports in this PR.

Type of change

From the following, please check the options that are relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] This change requires a documentation update

How has this been tested?

• [x] Tested all jobs by running them locally using https://github.com/nektos/act

Checklist:

• [x] This contribution follows the project's code of conduct
• [x] This contribution follows the project's contributing guidelines
• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [ ] ~Any dependent changes have been merged and published in downstream modules~