Added GH Action

[vkatsuba]

Purposes of changes:

• Provided base GitHub Actions
• Added coveralls: used fork till merge/release https://github.com/markusn/coveralls-erl/pull/36
• Added elvis call to GH Actions
• Updated README.md: added GH Badges
• Remove .travis.yml
• Update rebar.config.script based on GH Actions
• Add rebar3 to .gitignore
• Fix error for GH Action when tests running - {'EXIT',nodistribution}
• Fix dialyzer warning:

  src/metrics/prometheus_quantile_summary.erl
  307: The created fun has no local return
  346: The created fun has no local return
  487: Function quantile_merge/2 has no local return
  491: Record construction #quantile_estimator{samples_count::number(),data_count::'undefined',inserts_since_compression::'undefined',data::[#group{v::number(),g::number(),delta::number(),rank::number()}],invariant::fun()} violates the declared type of field data_count::number() and inserts_since_compression::number()

GH Action Result: https://github.com/vkatsuba/prometheus.erl/actions/runs/788619303

[deadtrickster]

Great! could you please include elvis too?

[vkatsuba]

could you please include elvis too?

Done. GH Action Result: https://github.com/vkatsuba/prometheus.erl/runs/2447366977

[deadtrickster]

I just noticed a few changed unrelated to GH actions: src/metrics/prometheus_quantile_summary.erl test/eunit/collectors/vm/prometheus_vm_dist_collector_tests.erl

would be great to have them in a separate MR with short description, so I can proceed with this MR. Thanks!

[vkatsuba]

I just noticed a few changed unrelated to GH actions:

src/metrics/prometheus_quantile_summary.erl

test/eunit/collectors/vm/prometheus_vm_dist_collector_tests.erl

would be great to have them in a separate MR with short description, so I can proceed with this MR. Thanks!

The changes is related to dialyzer warnings. The dialyzer is a part of checking in GH Actions. I can remove it but I will also need to remove dialyzer call. Just for notes. The same about running tests in container, without those changes some tests will failed - I was provide this info in description. In other words all changes in current PR is related to GH actions and for tests/checking passing in containers.

[vkatsuba]

@deadtrickster I was divided to separate commits with short description. As I wrote above, they all refer to the current PR. So, please take a look if this approach with dividing commits is suite for you.