Draft: "Blog posts" instead of "News". Adapted Buttons at bottom of front page.

rename to blog posts, buttons according to https://gitlab.hzdr.de/hifis/overall/hifis.net/-/issues/310#note_1408462

• Filter for nothing anymore (yet "news")
• Decide on whether to remove "news" tag altogether; or instead remove only from some
• need to redirect all news links to corresponding posts links
• rss feed is still called news.xml, but I think that's fine.

_data/navigation.yml

@@ -78,8 +78,8 @@ header:
         url: "spotlights"
   - title: "Latest & Media"
     entries:
-      - title: "News"
-        url: "news/"
+      - title: "Blog Posts"
+        url: "posts"
       - title: "Upcoming events"
         url: "https://events.hifis.net/category/14/"
         external: True