[io grant] Document IO::Handle.DESTROY

Author: zoffixznet

doc/Type/IO/Handle.pod6

@@ -46,6 +46,19 @@ a dangling combiner. However, it also means that when the user inputs just an
 "e" and has no intention to also input a combining acute, your program will be
 waiting for another keypress before the initial "e" is returned.
 
+=head2 submethod DESTROY
+
+Defined as:
+
+    submethod DESTROY(IO::Handle:D:)
+
+Closes the filehandle. Note that garbage collection is not guaranteed to
+happen, so you must NOT rely on C<DESTROY> for closing the handles you
+I<write to> and instead close them yourself. Programs that open a lot of files
+should close the handles explicitly as well, regardless of whether they were
+open for writing, since too many files might get opened before garbage
+collection happens and the no longer used handles get closed.
+
 =head2 method eof
 
 Returns C<True> if the read operations have exhausted the content of the file.