Added docs for X::Proc::Unsuccessful

doc/Type/X/Proc/Unsuccessful.pod6

@@ -0,0 +1,17 @@
+=begin pod
+
+=TITLE class X::Proc::Unsuccessful
+
+=SUBTITLE Exception thrown if a Proc object is sunk after the process it ran exited unsuccessfully 
+
+    class X::Proc::Unsuccessful is Exception { ... }
+
+=head1 Methods
+
+=head2 method proc
+
+    method proc(X::Proc::Unsuccessful:D) returns Proc
+
+Returns the object that threw the exception.
+
+=end pod

type-graph.txt

@@ -274,6 +274,7 @@ class X::StubCode                   is Exception
 class X::Eval::NoSuchLang           is Exception
 class X::Seq::Consumed              is Exception
 class X::Caller::NotDynamic         is Exception
+class X::Proc::Unsuccessful         is Exception
 
 [Exceptions]
 # Exceptions: Numbers