docs(i18n): copy edits to internationalization cookbook (#2980)

* docs(i18n): copy edits

* docs(i18n): copy edit to data.json

* docs(i18n): Ward requested copy edits

Author: kapunahelewong

public/docs/ts/latest/cookbook/_data.json

@@ -48,7 +48,7 @@
 
   "i18n": {
     "title": "Internationalization (i18n)",
-    "intro": "Translate the app's template text into multiple languages"
+    "intro": "Translate the app's template text into multiple languages."
   },
 
   "set-document-title": {