Add skills doc #5675

Job	Run time
build-and-check	2m 44s
test-integration-packages/internal	1m 3s
test-integration-packages/billing	1m 12s
test-integration-cli	39s
test-integration-packages/agent-runtime	40s
test-integration-common	39s
test-integration-web	46s
test-integration-sdk	47s
test-sdk	49s
test-cli	50s
test-packages/internal	47s
test-packages/billing	39s
test-web	55s
test-packages/agent-runtime	48s
test-.agents	40s
test-common	48s
	14m 46s

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