Add update hook to update email body

I made the changes. Please check

Hii,

Changes seems fine.

A couple of small points. It's helpful to use a type hint comment so that IDEs know the class to use and can offer code completion and warn about missing functions.

Also, where a specific getter is available, we should use it rather than the generic get().

Fix those and we should be ready to merge.

@lostcarpark
Done with the changes. Please review :)

I've confirmed the needed changes have been made.
I've tested the update hook in a local environment, installed with the 1.0.0-alpha4 release, than checking out this branch and running the update script with Drush.
I have verified that the token was added to the email body as expected.
Moving back to RTBC, ready for merge.

Merged successfully. Thank you @lavanyatalwar and @nidhi27 for your work on this.
Moving to Fixed.

Automatically closed - issue fixed for 2 weeks with no activity.