add advent of svelte blog post (#1691)

* add advent of svelte blog post

* link

Author: Rich-Harris

apps/svelte.dev/content/blog/2025-12-01-advent-of-svelte-is-back.md

@@ -0,0 +1,13 @@
+---
+title: Advent of Svelte is back
+description: We've pivoted to video
+author: The Svelte team
+authorURL: https://svelte.dev/
+pinnedUntil: 2025-12-26
+---
+
+It's Advent of Svelte time!
+
+This year, we're doing something different: every day between now and Christmas, a new door will be unlocked on [advent.sveltesociety.dev/2025](https://advent.sveltesociety.dev/2025). Behind each door is a short video about a feature in Svelte that you might not have heard about, or a useful tip on how to get the most out of the framework.
+
+We're [kicking things off](https://advent.sveltesociety.dev/2025/1) with a demo of the [`$inspect(...)`](/docs/svelte/$inspect) rune. Check back every day for updates!