Document how to disable autosync for buildpacks

[briandealwis]

Description

With #4656 landing in Skaffold 1.14.0, we automatically enable autosync for buildpacks artifacts. This PR documents what file types are supported, and how to disable auto-sync.

[briandealwis]

FYI @russwolf

[codecov]

Codecov Report

Merging #4805 into master will decrease coverage by 0.21%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4805      +/-   ##
==========================================
- Coverage   71.82%   71.61%   -0.22%     
==========================================
  Files         347      348       +1     
  Lines       11869    12026     +157     
==========================================
+ Hits         8525     8612      +87     
- Misses       2725     2778      +53     
- Partials      619      636      +17     

Impacted Files	Coverage Δ
pkg/skaffold/build/tag/util.go	89.47% <0.00%> (-10.53%)	⬇️
pkg/skaffold/deploy/helm.go	74.61% <0.00%> (-2.54%)	⬇️
pkg/skaffold/debug/debug.go	38.59% <0.00%> (-2.15%)	⬇️
pkg/skaffold/runner/new.go	64.05% <0.00%> (-1.92%)	⬇️
pkg/skaffold/deploy/kustomize.go	76.19% <0.00%> (-0.24%)	⬇️
pkg/skaffold/kubectl/cli.go	100.00% <0.00%> (ø)
pkg/skaffold/deploy/kubectl/cli.go	87.34% <0.00%> (ø)
cmd/skaffold/app/cmd/filter.go	26.19% <0.00%> (ø)
pkg/skaffold/deploy/kubectl.go	66.00% <0.00%> (+0.26%)	⬆️
cmd/skaffold/app/cmd/cmd.go	65.89% <0.00%> (+0.26%)	⬆️
... and 3 more

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