Update description.md (#5981)

shared [this
document](https://docs.getdbt.com/reference/resource-properties/description#link-to-another-model-in-a-description)
and realized there was no URL description to added it for clarification
purposes.

[slack
thread](https://getdbt.slack.com/archives/C01F91XJ5PY/p1724838087603339?thread_ts=1724666191.420319&cid=C01F91XJ5PY)

website/docs/reference/resource-properties/description.md

@@ -1,7 +1,7 @@
 ---
 resource_types: all
 datatype: markdown_string
-
+description: "This guide explains how to use the description key to add YAML descriptions to dbt resources (models, sources, seeds) using markdown and Jinja for better documentation."
 ---
 
 <Tabs