website/docs: improve root page and redirect #25348

Job	Run time
lint-golint	44s
test-unittest	4m 45s
ci-outpost-mark	1s
build-container (proxy)	2m 59s
build-binary (proxy, linux, amd64)	1m 41s
build-container (ldap)	2m 43s
build-binary (proxy, linux, arm64)	2m 40s
build-container (radius)	2m 18s
build-binary (ldap, linux, amd64)	1m 52s
build-container (rac)	2m 15s
build-binary (ldap, linux, arm64)	2m 47s
build-binary (radius, linux, amd64)	2m 21s
build-binary (radius, linux, arm64)	1m 56s
build-binary (rac, linux, amd64)	3m 11s
build-binary (rac, linux, arm64)	1m 41s
	33m 54s

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