add vtarget and atarget

cereal/custom.capnp

@@ -197,6 +197,8 @@ struct LongitudinalPlanSP @0xf35cc4560bbf6ec2 {
       state @0 :AssistState;
       enabled @1 :Bool;
       active @2 :Bool;
+      vTarget @3 :Float32;
+      aTarget @4 :Float32;
     }
 
     enum Source {

sunnypilot/selfdrive/controls/lib/longitudinal_planner.py

@@ -113,5 +113,7 @@ class LongitudinalPlannerSP:
     assist.state = self.sla.state
     assist.enabled = self.sla.is_enabled
     assist.active = self.sla.is_active
+    assist.vTarget = float(self.sla.output_v_target)
+    assist.aTarget = float(self.sla.output_a_target)
 
     pm.send('longitudinalPlanSP', plan_sp_send)