Mention act user guide in act

[ChristopherHX]

We should mention where to find the act user guide and that documentation updates should target https://github.com/nektos/act-docs.

Please help me to improve the wording.

Maintainer see also https://github.com/nektos/act-maintainers/discussions/16

[github-actions]

🦙 MegaLinter status: ⚠️ WARNING

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ EDITORCONFIG	editorconfig-checker	2		0	0.01s
⚠️ MARKDOWN	markdownlint	2		1	0.6s
✅ REPOSITORY	gitleaks	yes		no	3.19s
✅ REPOSITORY	git_diff	yes		no	0.16s
✅ REPOSITORY	grype	yes		no	9.57s
✅ REPOSITORY	secretlint	yes		no	1.31s
✅ REPOSITORY	trivy-sbom	yes		no	0.69s
✅ REPOSITORY	trufflehog	yes		no	16.1s

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[codecov]

Codecov Report

Merging #1973 (4ab149f) into master (4989f44) will increase coverage by 0.83%.
Report is 225 commits behind head on master.
The diff coverage is 61.69%.

@@            Coverage Diff             @@
##           master    #1973      +/-   ##
==========================================
+ Coverage   61.22%   62.05%   +0.83%     
==========================================
  Files          46       52       +6     
  Lines        7141     8487    +1346     
==========================================
+ Hits         4372     5267     +895     
- Misses       2462     2799     +337     
- Partials      307      421     +114     

Files Changed	Coverage Δ
pkg/common/outbound_ip.go	0.00% <0.00%> (ø)
pkg/container/docker_cli.go	82.23% <ø> (ø)
pkg/container/docker_logger.go	52.08% <ø> (ø)
pkg/container/docker_volume.go	0.00% <0.00%> (ø)
pkg/container/file_collector.go	37.30% <0.00%> (ø)
pkg/container/host_environment.go	0.00% <0.00%> (ø)
...ontainer/linux_container_environment_extensions.go	23.07% <0.00%> (-1.25%)	⬇️
pkg/container/util.go	0.00% <0.00%> (ø)
pkg/exprparser/functions.go	66.32% <0.00%> (-1.04%)	⬇️
pkg/container/docker_run.go	13.45% <6.66%> (-0.13%)	⬇️
... and 29 more

... and 2 files with indirect coverage changes

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[chrowe]

Looks good to me!