docs: add kpt manifest.transform|validate functionality examples

[aaron-prindle]

Fixes #5094

[codecov]

Codecov Report

Merging #7870 (ed200d9) into main (290280e) will decrease coverage by 3.84%.
The diff coverage is 53.94%.

@@            Coverage Diff             @@
##             main    #7870      +/-   ##
==========================================
- Coverage   70.48%   66.63%   -3.85%     
==========================================
  Files         515      593      +78     
  Lines       23150    28716    +5566     
==========================================
+ Hits        16317    19136    +2819     
- Misses       5776     8174    +2398     
- Partials     1057     1406     +349     

Impacted Files	Coverage Δ
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/test.go	44.44% <0.00%> (ø)
cmd/skaffold/skaffold.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/inspect_tests.go	62.50% <14.28%> (-1.14%)	⬇️
cmd/skaffold/app/cmd/render.go	35.48% <18.18%> (-5.90%)	⬇️
cmd/skaffold/app/cmd/lsp.go	28.12% <28.12%> (ø)
cmd/skaffold/app/cmd/run.go	64.28% <33.33%> (-9.63%)	⬇️
cmd/skaffold/app/cmd/fix.go	56.41% <37.50%> (-20.07%)	⬇️
cmd/skaffold/app/cmd/verify.go	41.17% <41.17%> (ø)
... and 365 more

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