Add missing period at the end of a sentence (#13413)

Author: sevignator

contributors.yml

@@ -296,6 +296,7 @@
 - senseibarni
 - sergiodxa
 - serranoarevalo
+- sevignator
 - sgalhs
 - sgrishchenko
 - shamsup

docs/tutorials/address-book.md

@@ -344,7 +344,7 @@ Now the child route should be rendering through the outlet.
 
 ## Client Side Routing
 
-You may or may not have noticed, but when we click the links in the sidebar, the browser is doing a full document request for the next URL instead of client side routing, which completely remounts our app
+You may or may not have noticed, but when we click the links in the sidebar, the browser is doing a full document request for the next URL instead of client side routing, which completely remounts our app.
 
 Client side routing allows our app to update the URL without reloading the entire page. Instead, the app can immediately render new UI. Let's make it happen with [`<Link>`][link-component].