Add github actions testing

[snowe2010]

Add github actions testing and release process to move off of travis (which no longer works for this project)

[codecov]

Codecov Report

Merging #4 (7c4d574) into master (5673944) will not change coverage.
The diff coverage is 55.85%.

@@           Coverage Diff           @@
##           master       #4   +/-   ##
=======================================
  Coverage   56.88%   56.88%           
=======================================
  Files          11       11           
  Lines         327      327           
=======================================
  Hits          186      186           
  Misses        141      141           

Impacted Files	Coverage Δ
test/help_test.rb	46.15% <28.57%> (ø)
test/fylla_test.rb	40.00% <33.33%> (ø)
test/zsh/completion_option_test.rb	52.30% <47.61%> (ø)
test/zsh/completion_test.rb	45.45% <50.00%> (ø)
test/zsh/enum_test.rb	52.27% <54.54%> (ø)
test/zsh/completion_flag_test.rb	54.28% <55.55%> (ø)
test/zsh/options_test.rb	55.22% <58.33%> (ø)
test/zsh/weird_descriptions_test.rb	57.69% <66.66%> (ø)
test/zsh/test_commands/plain_subcommand.rb	85.71% <71.42%> (ø)
test/bash/bash_clis/cli.rb	84.00% <72.72%> (ø)
... and 1 more