[Feature request]: add email template for user activated by admin

[Jimmi08]

Motivation

Possibility to style and customize the email that is already sent

Proposed Solution

Add a standard email template - like when the user is created by admin

Alternatives

The content of email is now hardcoded:

$message = USRLAN_114." ".$row['user_name'].",\n\n".USRLAN_122." ".SITENAME.".\n\n".USRLAN_123."\n\n";
				$message .= str_replace("{SITEURL}", SITEURL, USRLAN_139);

Additional Context

No response