ci: add changelog link in releases (#1123)

.github/workflows/release-tag.yml

@@ -20,4 +20,4 @@ jobs:
         with:
           tag_name: ${{ github.ref }}
           body: |
-            Please refer to CHANGELOG.md for details.
+            Please refer to [CHANGELOG.md](https://github.com/vuejs/vue-next/blob/master/CHANGELOG.md) for details.