feat: add json logger output

[KnisterPeter]

This will allow to format log output as json.
This is helpful in cases where act is not executed on a 'local' machine.

[codecov]

Codecov Report

Merging #1026 (b0f8726) into master (4f8da0a) will increase coverage by 1.07%.
The diff coverage is 80.37%.

@@            Coverage Diff             @@
##           master    #1026      +/-   ##
==========================================
+ Coverage   57.50%   58.58%   +1.07%     
==========================================
  Files          32       34       +2     
  Lines        4594     4648      +54     
==========================================
+ Hits         2642     2723      +81     
+ Misses       1729     1696      -33     
- Partials      223      229       +6     

Impacted Files	Coverage Δ
pkg/model/action.go	0.00% <ø> (ø)
pkg/model/planner.go	50.73% <ø> (+0.32%)	⬆️
pkg/runner/logger.go	61.76% <64.70%> (-3.67%)	⬇️
pkg/exprparser/interpreter.go	72.79% <66.66%> (-0.61%)	⬇️
pkg/runner/runner.go	74.52% <75.00%> (-1.95%)	⬇️
pkg/runner/expression.go	89.36% <77.61%> (-1.46%)	⬇️
pkg/runner/job_executor.go	81.57% <81.57%> (ø)
pkg/runner/step_context.go	85.81% <84.00%> (+4.17%)	⬆️
pkg/runner/action.go	84.21% <84.21%> (ø)
pkg/runner/run_context.go	80.03% <96.15%> (+0.38%)	⬆️
... and 8 more

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[ChristopherHX]

Nice to have, it works :)

[ChristopherHX]

Note: I wondered why I see a Error: <errmsg> line after a failure, which ignored the logrus logger / json formatter. It seems that cobra cli prints it if we return the error back to the library, here the callback which causes the printed line when error != nil

act/cmd/root.go

Line 158 in 3db3c73

return func(cmd *cobra.Command, args []string) error {