chore: add docs to explain keep-running-on-failure

[ericzzzzzzz]

Fixes: #8342
Related: Relevant tracking issues, for context
Merge before/after: Dependent or prerequisite PRs

Description

User facing changes (remove if N/A)

Follow-up Work (remove if N/A)

[ericzzzzzzz]

wanna to try skip running tests when prs are only about docs chanegs...will create an issue for test

[codecov]

Codecov Report

Merging #8446 (7b2e955) into main (290280e) will decrease coverage by 5.29%.
The diff coverage is 55.02%.

@@            Coverage Diff             @@
##             main    #8446      +/-   ##
==========================================
- Coverage   70.48%   65.19%   -5.29%     
==========================================
  Files         515      603      +88     
  Lines       23150    29898    +6748     
==========================================
+ Hits        16317    19493    +3176     
- Misses       5776     8928    +3152     
- Partials     1057     1477     +420     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/completion.go	13.04% <0.00%> (-1.25%)	⬇️
cmd/skaffold/app/cmd/config/list.go	65.21% <ø> (ø)
cmd/skaffold/app/cmd/config/set.go	88.72% <ø> (ø)
cmd/skaffold/app/cmd/config/util.go	54.28% <ø> (ø)
cmd/skaffold/app/cmd/credits.go	100.00% <ø> (ø)
cmd/skaffold/app/cmd/credits/export.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/deploy.go	40.90% <0.00%> (-12.94%)	⬇️
cmd/skaffold/app/cmd/generate_pipeline.go	60.00% <ø> (ø)
cmd/skaffold/app/cmd/inspect_modules.go	65.00% <ø> (ø)
cmd/skaffold/app/cmd/inspect_profiles.go	66.66% <ø> (ø)
... and 426 more

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[aaron-prindle]

LGTM!