Creates a migration guide.

The general idea is to provide advice on how to migrate
an existing application over to Symfony using some
proven approaches.

The page should provide around 3 alternatives and some
discussion when they might be suitable as well as
additional resources like videos on this topics from
the official Symfony YouTube-channel.

Author: Denis Brumann

index.rst

@@ -44,6 +44,7 @@ Topics
     logging
     mercure
     messenger
+    migration
     performance
     profiler
     routing