Add translation for forum Subject fields [Risolto]

A recent posting: https://en.numista.com/forum/topic168595.html

There's a button to translate the text of the post, but it takes extra effort to translate the Subject field. The forum would be improved if there was a translate button for the Subject or, even better, if the Subject field was translated when the post was translated.

 I think it has now been implemented - I tried just now on a topic [see below] 

that not only translated the message, but just above it was the Subject translated in bold. 

Sorry I forgot to follow up here. I confirm this was implemented. The subject is now included when translating the first post of a topic, as seen on ZacUK's screenshot.