Update feature3.md with blog post link

Added a link to learn more about collections.

Author: scottjenson

data/roadmap/feature3.md

@@ -3,4 +3,4 @@ title: Collections
 status: next
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-4.6 Users and admins can create a collection of accounts they recommend. This allows both new and existing user to easily follow a range of curated users quickly.
+4.6 Users and admins can create a collection of accounts they recommend. This allows both new and existing user to easily follow a range of curated users quickly. [Learn more.](https://blog.joinmastodon.org/2025/10/our-ideas-about-packs/)