Document checking whether a process on another node is alive (#13854)

Author: nathanl

lib/elixir/lib/process.ex

@@ -88,6 +88,9 @@ defmodule Process do
   `false`.
 
   `pid` must refer to a process running on the local node or `ArgumentError` is raised.
+  To check whether a process on any node is alive you can use the [`:erpc`](`:erpc`) module.
+
+      :erpc.call(node(pid), Process, :alive?, [pid])
 
   Inlined by the compiler.
   """