Give details on how to work with HTML tags inside front-end translations

[miaulalala]

Things such as placeholders, and other tricks like how to use tags (ErrorMessageFactory.js uses a trick with replace() for example).

[ChristophWurst]

Ref https://github.com/nextcloud/mail/blob/124c45ccb4bc62991b741beaf12d8b87dc5b9566/src/util/ErrorMessageFactory.js#L34-L44