Fix empty changelog field for analytics extension

Set the analytics extension changelog to the GitHub releases page instead of
an empty string, which the catalog treats as a URI when present and can fail
schema validation and downstream tooling.

Assisted-by: GitHub Copilot (model: Claude Opus 4.8, autonomous)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: mnriem

extensions/catalog.community.json

@@ -155,7 +155,7 @@
       "repository": "https://github.com/Fyloss/spec-kit-analytics",
       "homepage": "https://github.com/Fyloss/spec-kit-analytics",
       "documentation": "https://github.com/Fyloss/spec-kit-analytics/tree/main/doc",
-      "changelog": "",
+      "changelog": "https://github.com/Fyloss/spec-kit-analytics/releases",
       "license": "MIT",
       "category": "visibility",
       "effect": "read-write",