Added an additional log to notify shutdown start

- there can now be quite a big delay between SIGINT/TERM being received and shutdown finishing
- add an extra log message to acknowledge the SIGINT/TERM to facilitate debugging and just be clear

core/server/ghost-server.js

@@ -115,6 +115,7 @@ class GhostServer {
 
             async function shutdown() {
                 try {
+                    logging.warn(i18n.t('notices.httpServer.ghostIsShuttingDown'));
                     await self.stop();
                     process.exit(0);
                 } catch (error) {

core/server/translations/en.json

@@ -650,6 +650,7 @@
             "ghostIsRunningIn": "Ghost is running in {env}...",
             "listeningOn": "Listening on: {host}:{port}",
             "urlConfiguredAs": "Url configured as: {url}",
+            "ghostIsShuttingDown": "Ghost is shutting down",
             "ghostHasShutdown": "Ghost has shut down",
             "yourBlogIsNowOffline": "Your site is now offline",
             "ghostWasRunningFor": "Ghost was running for"