hammerspoon: add news entry

assets/javascripts/news.json

@@ -1,4 +1,8 @@
 [
+  [
+    "2024-01-12",
+    "New documentation: <a href=\"/hammerspoon/\">Hammerspoon</a>"
+  ],
   [
     "2024-01-05",
     "New documentation: <a href=\"/bazel/\">Bazel</a>"