index: add Bluesky link

Mention Go's Bluesky account where various announcement posts get made.

Also linkify Mastodon's hashtag mention while here.

For golang/go#71319.

Change-Id: I6a3af25c8c66d8015560ac6db3a1a1b8f6e892c2
Reviewed-on: https://go-review.googlesource.com/c/wiki/+/755220
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Marc Dougherty <muncus@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

index.md

diff --git a/index.md b/index.md
index 0c05d6d..4f4058a 100644
--- a/index.md
+++ b/index.md
@@ -98,7 +98,8 @@
   - [Gophers Slack Channel](http://gophers.slack.com/) - For real-time chat ([request membership](http://blog.gopheracademy.com/gophers-slack-community/)).
   - [Golang News](http://golangnews.com) - For curated links about Go Programming.
   - There is also a [/r/golang](http://reddit.com/r/golang) sub-reddit.
-  - On Mastodon, follow the <a rel="me noreferrer" href="https://hachyderm.io/@golang" target="_blank">@golang</a> account and keep tabs on the #golang hashtag.
+  - On Bluesky, follow the [@golang.org](https://bsky.app/profile/golang.org) account and keep tabs on the [#golang](https://bsky.app/hashtag/golang) hashtag.
+  - On Mastodon, follow the <a rel="me noreferrer" href="https://hachyderm.io/@golang" target="_blank">@golang</a> account and keep tabs on the [#golang](https://hachyderm.io/tags/golang) hashtag.
   - On Twitter, follow the [@golang](https://twitter.com/golang) account and keep tabs on the [#golang](https://twitter.com/search?q=%23golang&src=typd) hashtag.
   - We've also got a landing page on [Stack Overflow](http://stackoverflow.com/tags/go) for Go Q&A.
   - Matrix enthusiasts are invited to join [#go-lang:matrix.org](https://matrix.to/#/#go-lang:matrix.org) or the gophers space [#gophers:dendrite.matrix.org](https://matrix.to/#/#gophers:dendrite.matrix.org).