feat: cache notices to reduce frequency of upgrade notifications

[cplee]

Look for ETag header when checking for upgrade notices and store that value in ~/.cache/act/.notices.etag. Use that value as If-None-Match header to perform conditional GET request.

[mergify]

@cplee this pull request has failed checks 🛠

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ EDITORCONFIG	editorconfig-checker	1		0	0.01s
✅ REPOSITORY	gitleaks	yes		no	3.05s
✅ REPOSITORY	git_diff	yes		no	0.0s
✅ REPOSITORY	secretlint	yes		no	1.41s

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[codecov]

Codecov Report

Merging #1592 (4e291e0) into master (4989f44) will increase coverage by 0.71%.
The diff coverage is 77.40%.

@@            Coverage Diff             @@
##           master    #1592      +/-   ##
==========================================
+ Coverage   61.22%   61.93%   +0.71%     
==========================================
  Files          46       46              
  Lines        7141     7185      +44     
==========================================
+ Hits         4372     4450      +78     
+ Misses       2462     2428      -34     
  Partials      307      307              

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	13.58% <ø> (ø)
pkg/container/docker_volume.go	0.00% <ø> (ø)
pkg/runner/run_context.go	78.81% <0.00%> (ø)
pkg/container/docker_images.go	27.02% <29.41%> (-4.13%)	⬇️
pkg/container/docker_auth.go	51.35% <56.25%> (+3.73%)	⬆️
pkg/runner/runner.go	86.45% <66.66%> (-2.05%)	⬇️
pkg/common/git/git.go	57.72% <79.71%> (+7.72%)	⬆️
... and 11 more

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