website: document http check timeout configuration

website/source/docs/agent/checks.html.markdown

@@ -26,7 +26,10 @@ There are three different kinds of checks:
   every 30 seconds) to the specified URL. The status of the service depends on the HTTP response code:
   any `2xx` code is considered passing, a `429 Too Many Requests` is a warning, and anything else is a failure.
   This type of check should be preferred over a script that uses `curl` or another external process
- to check a simple HTTP operation.
+  to check a simple HTTP operation. By default, HTTP checks will be configured
+  with a request timeout equal to the check interval, with a max of 10 seconds.
+  It is possible to configure a custom HTTP check timeout value by specifying
+  the `timeout` field in the check definition.
 
 * Time to Live (TTL) - These checks retain their last known state for a given TTL.
   The state of the check must be updated periodically over the HTTP interface. If an
@@ -59,7 +62,8 @@ A HTTP check:
     "id": "api",
     "name": "HTTP API on port 5000",
     "http": "http://localhost:5000/health",
-    "interval": "10s"
+    "interval": "10s",
+    "timeout": "1s"
   }
 }
 ```