feat(policy): add system load average as checker input

Signed-off-by: Xe Iaso <me@xeiaso.net>

lib/policy/celchecker.go

@@ -102,6 +102,12 @@ func (cr *CELRequest) ResolveName(name string) (any, bool) {
 		return expressions.URLValues{Values: cr.URL.Query()}, true
 	case "headers":
 		return expressions.HTTPHeaders{Header: cr.Header}, true
+	case "load_1m":
+		return expressions.Load1(), true
+	case "load_5m":
+		return expressions.Load5(), true
+	case "load_15m":
+		return expressions.Load15(), true
 	default:
 		return nil, false
 	}