Migration to GitHub Actions

[sunkan]

Here is first working draft of migration to github actions

I hade to disable nightly builds because of phpspec/prophecy not supporting nightly.

I also added a build step to verify that it works with --prefer-lowest composer option

You can see the output from the last build here
https://github.com/sunkan/openapi-psr7-validator/actions/runs/415797193

[scaytrase]

I hade to disable nightly builds because of phpspec/prophecy not supporting nightly.

That's the purpose of allow-failures for nighly. To keep track of things that are not working.Is it possible to have it, but non-blocking?

[sunkan]

@scaytrase

I've updated the action with nightly that is none blocking.

you can see the output here https://github.com/sunkan/openapi-psr7-validator/actions/runs/415935071

I also reworked the highest/lowest version testing

[scaytrase]

looks nice

[sunkan]

I think this is finished to merge if you approve

[scaytrase]

Thanks @sunkan