Update when-to-use.mdx

Noting there is no Observability for Snippets.
I wish our docs had an Observability overview, so I linked it to the Logs overview.

Author: cf-scott

src/content/docs/rules/snippets/when-to-use.mdx

@@ -44,6 +44,7 @@ Snippets are ideal for fast, cost-free request and response modifications at the
 - Deep integrations with [Developer Platform](/learning-paths/workers/devplat/intro-to-devplat/) services like [Durable Objects](/durable-objects/) or [D1](/d1/).
 - Use cases requiring advanced runtime features, such as:
   - [Environment variables](/workers/configuration/environment-variables/)
+  - [Observability] (/workers/observability/logs/)
   - [Bindings](/workers/runtime-apis/bindings/)
   - [Cron triggers](/workers/configuration/cron-triggers/)
   - High [compute limits](/rules/snippets/#limits)