doc: add space after period

child_process IPC channel note

PR-URL: nodejs/node#16334
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>

doc/api/child_process.md

@@ -646,8 +646,8 @@ spawn('prg', [], { stdio: ['pipe', null, null, null, 'pipe'] });
 parent and child processes, and the child is a Node.js process, the child
 is launched with the IPC channel unreferenced (using `unref()`) until the
 child registers an event handler for the [`process.on('disconnect')`][] event
-or the [`process.on('message')`][] event.This allows the child to exit normally
-without the process being held open by the open IPC channel.*
+or the [`process.on('message')`][] event. This allows the child to exit
+normally without the process being held open by the open IPC channel.*
 
 See also: [`child_process.exec()`][] and [`child_process.fork()`][]