docs: add note about cncf to readme #5254

Job	Run time
check_format_and_unit_tests	1m 13s
build / Special integration tests (24)	1m 43s
build / Special integration tests (17)	1m 54s
build / Special integration tests (21)	1m 44s
build / httpclient-tests (vertx) / Integration tests (24, 1.32.0, vertx)	22m 8s
build / httpclient-tests (jetty) / Integration tests (24, 1.32.0, jetty)	22m 11s
build / httpclient-tests (jdk) / Integration tests (24, 1.32.0, jdk)	22m 22s
build / integration_tests (21, 1.33.0) / Integration tests (21, 1.33.0, vertx)	23m 7s
build / integration_tests (24, 1.30.12) / Integration tests (24, 1.30.12, vertx)	22m 37s
build / integration_tests (21, 1.30.12) / Integration tests (21, 1.30.12, vertx)	21m 26s
build / integration_tests (21, 1.31.8) / Integration tests (21, 1.31.8, vertx)	23m 32s
build / integration_tests (24, 1.32.4) / Integration tests (24, 1.32.4, vertx)	22m 50s
build / integration_tests (17, 1.30.12) / Integration tests (17, 1.30.12, vertx)	21m 58s
build / integration_tests (17, 1.33.0) / Integration tests (17, 1.33.0, vertx)	24m 11s
build / integration_tests (24, 1.33.0) / Integration tests (24, 1.33.0, vertx)	23m 13s
build / integration_tests (17, 1.31.8) / Integration tests (17, 1.31.8, vertx)	23m 34s
build / integration_tests (21, 1.32.4) / Integration tests (21, 1.32.4, vertx)	22m 37s
build / integration_tests (17, 1.32.4) / Integration tests (17, 1.32.4, vertx)	22m 39s
build / integration_tests (24, 1.31.8) / Integration tests (24, 1.31.8, vertx)	23m 12s
	5h 48m 11s

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