The option to add a custom website signature can now be added easily in the General Settings section of the admin.
The "General" tab of the General Settings section can be used to add a signature for the default system emails.
This section will only edit the default website emails. There is also an option to add a different signature for the admin operator in the admin settings. More information on this in the link below.
FROALA Text Editor: Versions and their Upload Functionalities