Changed content of "recent news" menu
The "Missives" menu had no purpose since nothing has been put in there for a long time (related: #249 (closed)). i removed it and replaced it with "announcements", a new tag used to show announcements and main news. I think this would make easier for newcomer and curious to look for recent big upgrades or changes. Of course, that requires to write a blog post when something big happens :D.
- created tag "announcements"
- replace "Missives" with "Announcements" and linked to related tag
- moved "All Posts" at the bottom of the submenu
- add tag 'announcements' to blog posts that need it