Improve XDG Spec supporting

[tony-sol]

Switch from direct using of XDG_CONFIG_HOME env variable to adrg/xdg lib.

Now, it will be support xdg across windows/darwin/unix platforms and looks for config file like:

~/.actrc
"${XDG_CONFIG_HOME}/act/actrc"
"${XDG_CONFIG_HOME}/.actrc"
./.actrc

[codecov]

Codecov Report

Merging #1656 (fc95fad) into master (4989f44) will increase coverage by 1.26%.
The diff coverage is 71.47%.

@@            Coverage Diff             @@
##           master    #1656      +/-   ##
==========================================
+ Coverage   61.22%   62.49%   +1.26%     
==========================================
  Files          46       48       +2     
  Lines        7141     7452     +311     
==========================================
+ Hits         4372     4657     +285     
- Misses       2462     2476      +14     
- Partials      307      319      +12     

Impacted Files	Coverage Δ
pkg/container/docker_cli.go	82.23% <ø> (ø)
pkg/container/docker_logger.go	52.08% <ø> (ø)
pkg/container/docker_pull.go	33.33% <ø> (ø)
pkg/container/docker_run.go	14.08% <ø> (+0.49%)	⬆️
pkg/container/docker_volume.go	0.00% <ø> (ø)
pkg/container/file_collector.go	37.30% <0.00%> (ø)
pkg/container/host_environment.go	0.00% <0.00%> (ø)
pkg/model/workflow.go	42.11% <ø> (ø)
pkg/model/planner.go	44.71% <21.27%> (-4.12%)	⬇️
pkg/container/docker_images.go	27.02% <29.41%> (-4.13%)	⬇️
... and 29 more

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[mrnossiom]

It seems that even though act looks for config files in these dirs, it still writes the default config to ~/.actrc