docs: add documentation for webhook #2533

Job	Run time
create-version	3s
test-pyfunc-server (3.8)	3m 49s
build-ui	1m 55s
test-pyfunc-server (3.9)	3m 36s
test-pyfunc-server (3.10)	3m 43s
lint-api	1m 26s
test-api	3m 48s
test-batch-predictor (3.8)	39s
test-batch-predictor (3.9)	40s
test-observation-publisher	50s
test-batch-predictor (3.10)	36s
test-python-sdk (3.8)	58s
test-python-sdk (3.9)	57s
test-python-sdk (3.10)	55s
build-inference-logger	1m 31s
build-transformer	2m 21s
build-batch-predictor-base-image	3m 27s
build-observation-publisher	2m 9s
build-pyfunc-server-base-image	2m 29s
build-api	2m 23s
e2e-test	13m 1s
release / publish-api	15s
release / publish-merlin-pyfunc-server	0s
release / publish-python-sdk	0s
release / publish-merlin-batch-predictor	0s
release / publish-inference-logger	12s
release / publish-transformer	14s
release / publish-batch-predictor-base-image	1m 42s
release / publish-observation-publisher	1m 20s
release / publish-pyfunc-server-base-image	58s
release / publish-python-sdk-docker	0s
	55m 57s

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