Documented /healthy, /ready API for alertmanager (#1445)
Documented /healthy, /ready API for alertmanager (#1445)

Add document for alertnamager about some management api including the following:
/-/healthy
/-/ready
/-/reload

Signed-off-by: Lvjiawei <29ca26d42d0b6acadd5b29654b9a7a859f18982b@cmss.chinamobile.com>
prometheus/docs,prometheus/docs,prometheus/docs