Github actions

[AlexEne]

💡 Feature Description

We could move to github actions for CI use it for testing all 3 platforms without requiring travis and appveyor accounts.

To support windows, this requires rewriting the current ci/script.sh to be platform agnostic. I've noticed wasmtime uses a rust runner. The benefit of that woudld be that windows contirbutors can run tests locally without requiring WSL (or something similar).

Explanation of the requested feature. What use case does it solve?
Windows & Linux tests could be unified

🙌 Are you interested in implementing this feature?

• Yes

[AlexEne]

Only remaining things are:

• Publish docs updates
• Test on windows
• Test on osx