add kill + example code

scheduler.kill seems like its not implemented comletly or doest work as
expected.

kernel/syscall/handler.cc

@@ -66,6 +66,9 @@ extern "C" size_t syscall_handler(size_t sysnum, size_t p1, size_t p2,
          case Syscall::ID::SYS_EXIT:
             Syscall::Skeleton::exit(Guard::enter().vault());
             return 0;
+         case Syscall::ID::SYS_KILL:
+            Syscall::Skeleton::kill(Guard::enter().vault(),p1);
+            return 0;
      }
 
 	return static_cast<size_t>(-1);

kernel/syscall/skeleton.cc

@@ -108,5 +108,8 @@ void exit(Vault &vault) {
     vault.scheduler.exit();
 }
 
+void kill(Vault &vault, size_t pid){
+    vault.scheduler.kill(&apps[pid]);
+}
 }  // namespace Skeleton
 }  // namespace Syscall

kernel/syscall/stub.h

@@ -16,7 +16,7 @@ enum class ID : size_t {
     SEM_SIGNAL=7,
     SYS_GETPID = 8,
     SYS_EXIT = 9,
-    //SYS_KILL=10
+    SYS_KILL = 10
 };
 }  // namespace Syscall
 
@@ -67,3 +67,7 @@ extern "C" ssize_t sys_safe_call(Syscall::ID id, size_t p1, size_t p2,
     sys_call(Syscall::ID::SYS_EXIT, 0, 0, 0, 0, 0);
 }
 
+[[gnu::always_inline]] static inline void sys_kill(size_t pid){
+    sys_call(Syscall::ID::SYS_KILL, pid, 0, 0, 0, 0);
+}
+