Add the Gizmo look for announcements: framed boxes that share a row

gizmolab's "next event" and "next assembly" boxes were hand-written HTML in
the home page's intro; they are announcements by nature, so now they can
be: a fourth style, a box framed in the theme's link colour with an italic
heading. Headed Gizmo boxes in the same spot share a row on wide screens
(the notices wrapper is a flex row, stacking on old browsers like .cols);
one without a heading takes the whole row, which is how a banner line goes
above a pair of boxes.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sd8UPWrvyYCLj97JexNw3A

1 files changed, 2 insertions, 1 deletions

diff --git a/README.md b/README.md
index df35621..828ff20 100644
--- a/README.md
+++ b/README.md
@@ -15,7 +15,8 @@ Server-rendered HTML, no JavaScript required, works on old browsers and phones.
   them by kind with search, rename and delete. Uploads are 10 MB per file by default;
   the superadmin can set a different limit per blog.
 - **Announcements**: blog-wide notices (next meeting, this month's book, a closure)
-  shown at the top or bottom of the main content or of a side column; each can be hidden without deleting.
+  shown at the top or bottom of the main content or of a side column — highlighted, as a
+  warning, plain, or as framed "Gizmo" boxes that sit side by side; each can be hidden without deleting.
 - Every blog has **pages** (Home, About, News, …); each page holds posts, with an
   optional text before them (an intro) and after them (a site map, a widget). Posts can
   carry **tags**, shown under the date; each tag has its own page listing every post