N20: Add discussion links

Author: ozkriff

content/posts/newsletter-020/index.md

@@ -1492,12 +1492,10 @@ Want something mentioned in the next newsletter?
 Also, subscribe to [@rust_gamedev on Twitter][@rust_gamedev]
 or [/r/rust_gamedev subreddit][/r/rust_gamedev] if you want to receive fresh news!
 
-<!--
-TODO: Add real links and un-comment once this post is published
-**Discussions of this post**:
-[/r/rust](TODO),
-[twitter](TODO).
--->
+**Discuss this post on**:
+[/r/rust](https://reddit.com/r/rust/comments/mo72tu/this_month_in_rust_gamedev_20_march_2021),
+[Twitter](https://twitter.com/rust_gamedev/status/1380907528201076741),
+[Discord](https://discord.gg/yNtPTb2).
 
 [/r/rust_gamedev]: https://reddit.com/r/rust_gamedev
 [@rust_gamedev]: https://twitter.com/rust_gamedev