docs: add sample command for Windows

Author: kenjis

user_guide_src/source/dbmgmt/migration.rst

@@ -128,8 +128,12 @@ You can use (migrate) with the following options:
 
 This example will migrate ``Acme\Blog`` namespace with any new migrations on the test database group::
 
+    For Unix:
     > php spark migrate -g test -n Acme\\Blog
 
+    For Windows:
+    > php spark migrate -g test -n Acme\Blog
+
 When using the ``--all`` option, it will scan through all namespaces attempting to find any migrations that have
 not been run. These will all be collected and then sorted as a group by date created. This should help
 to minimize any potential conflicts between the main application and any modules.