Fix docker: invalid reference format

[ChristopherHX]

Added a test to enshure that docker actions with names ending by anything which matches against [^a-zA-Z0-9] will still generate a valid docker container name.

./test_ would get image name like act-test-:latest => docker fails without this change

Fixes #744
Fixes #756

[codecov]

Codecov Report

Merging #767 (079c8ae) into master (0f04942) will increase coverage by 4.79%.
The diff coverage is 64.06%.

@@            Coverage Diff             @@
##           master     #767      +/-   ##
==========================================
+ Coverage   49.27%   54.06%   +4.79%     
==========================================
  Files          23       23              
  Lines        2401     2658     +257     
==========================================
+ Hits         1183     1437     +254     
+ Misses       1090     1074      -16     
- Partials      128      147      +19     

Impacted Files	Coverage Δ
pkg/container/docker_build.go	0.00% <0.00%> (ø)
pkg/container/docker_run.go	1.83% <0.00%> (-0.10%)	⬇️
pkg/common/git.go	52.85% <30.15%> (-6.94%)	⬇️
pkg/runner/runner.go	68.96% <33.33%> (-7.51%)	⬇️
pkg/model/planner.go	51.85% <41.37%> (+18.76%)	⬆️
pkg/model/workflow.go	51.08% <62.68%> (+25.37%)	⬆️
pkg/container/docker_pull.go	36.17% <64.70%> (+17.98%)	⬆️
pkg/runner/expression.go	85.38% <71.87%> (-1.26%)	⬇️
pkg/runner/step_context.go	78.37% <79.03%> (+9.43%)	⬆️
pkg/runner/run_context.go	80.36% <98.55%> (+3.95%)	⬆️
... and 7 more

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