Allow an actor to be startet from anywhere

emper/Actor.hpp

 // SPDX-License-Identifier: LGPL-3.0-or-later
-// Copyright © 2020 Florian Schmaus
+// Copyright © 2020 Florian Schmaus, Florian Fischer
 #pragma once
 
 #include <atomic>
 #include <chrono>
 
+#include "CallerEnvironment.hpp"
 #include "Fiber.hpp"
 #include "UnboundedBlockingMpscQueue.hpp"
 
@@ -55,12 +56,19 @@ class Actor {
 	void stop() { setState(Stopped); }
 
  public:
+	template <CallerEnvironment callerEnvironment = CallerEnvironment::EMPER>
 	void start() {
 		if (state.load(std::memory_order_acquire) != Stopped) return;
 
 		Fiber* actorFiber = Fiber::from(std::bind(&Actor::actorLoop, this));
+		if constexpr (callerEnvironment == CallerEnvironment::EMPER) {
 			runtime.schedule(*actorFiber);
+		} else {
+			runtime.scheduleFromAnywhere(*actorFiber);
 		}
+	}
+
+	void startFromAnywhere() { start<CallerEnvironment::ANYWHERE>(); }
 
 	void tell(T t) { queue.put(t); }