Document behaviour and caveats due to sunk unsuccessful Proc

Author: zoffixznet

doc/Type/Proc.pod6

@@ -74,6 +74,11 @@ of a newline is.
 If C<$merge> is set to True, the standard output and error stream end up
 merged in C<$proc.out>.
 
+=head2 method sink
+
+When sunk, the C<Proc> object will throw L<X::Proc::Unsuccessful>
+if the process it run exited unsuccessfully.
+
 =head2 method spawn
 
     method spawn(Proc:D *@args ($, *@), :$cwd = $*CWD, Hash() :$env = %*ENV) returns Bool:D

doc/Type/Proc/Async.pod6

@@ -125,6 +125,17 @@ called before, an exception of L<type
 X::Proc::Async::AlreadyStarted|/type/X::Proc::Async::AlreadyStarted> is
 thrown.
 
+Note: If you wish to C<await> the Promise and discard its result, using
+
+    try await $p.start;
+
+B<will throw> if the program exited with non-zero status, as the C<Proc>
+returned as the result of the Promise throws when sunk and in this case it
+will get sunk outside the C<try>. To avoid that, sink it yourself I<inside> the
+C<try>:
+
+    try sink await $p.start;
+
 =head2 method started
 
     method started(Proc::Async:D:) returns Bool:D