T7253: Improve documentation about upgrades with recommendations

Improve the documentation about upgrades and rollbacks with information about how to handle settings.

content/designs/system-updates-and-rollback.md

@@ -742,7 +742,7 @@ and the signature is checked for the extracted commit tree.
 
 ### Configuration
 
-As described in [preferences and persistence]( {{< ref preferences-and-persistence.md >}} )
+As described in [preferences and persistence]( {{< ref "preferences-and-persistence.md" >}} )
 there different types of settings which should be preserved across updates by
 either keeping them intact of updating them to match the new logic of the
 application.
@@ -758,14 +758,14 @@ which modifies the read-only partitions, but does not modify the read-write
 ones. To handle the upgrade of system settings stored in `/etc` a copy of its
 default values is kept in `/usr/etc` which is updated with the new commit.
 Thanks to this information `OSTree` can detect the files that have been changed
-and apply a 3-way merge, to update the `/etc`.
+and apply a 3-way merge, to update `/etc`.
 
-This process allows to update settings to new defaults for files that were not
+This process allows settings to be updated to new defaults where files are not
 modified and keep intact those that were.
 
 Applications are encouraged to handle settings adaptation to new version
 following the guidelines described in [user and user data management]( {{< ref "#user-and-user-data-management" >}} )
-and [preference and persistence]( {{< ref preferences-and-persistence.md >}} ).
+and [preference and persistence]( {{< ref "preferences-and-persistence.md" >}} ).
 
 ### Error handling