add 'improve translation' button to the manual translation pages

I'd like to have a button to 'improve translation' added on the content pages of the manual, to help on the maintenance of the translations we have already released. Many times we release translations because they are complete, but when we update the pages the translations get outdated and we end up having very few translations.

I think if we give other readers the opportunity to maintain the translation, we will have more contributors per language and we will make it easier for translators to make a good translation, as they will be able to go back and forth from the translation platform to the website.