add rspec github annotations formatter

[jessereynolds]

This adds rspec-gibhub annotations formatter as second rspec formatter when running under github actions. progress formatter is retained as it gives stack traces on errors.

This allows surfacing of errors on the summary screen avoiding the need to drill into the log (however that will still be useful to get stack traces).

On the summary screen, before:

after:

On the test output details view before:

after: