Forums page with instructions

Author: StrangeWill

_data/navigation.yml

@@ -4,7 +4,7 @@
 - title: Slack
   url: /slack/
 - title: Forums
-  url: https://forums.devanooga.com/
+  url: /forums/
 - title: Blog
   url: /blog/
 - title: Community

_pages/forums.md

@@ -1,7 +1,17 @@
 ---
+layout: page
 title: Forums
-external_url: https://forums.devanooga.com/
-menu_group: 1
-menu_sort: 4
-description: "The devanooga forums — longer-form discussion for the Chattanooga developer community."
----
+description: "The devanooga forums for longer-form discussion in the Chattanooga developer community."
+permalink: /forums/
+---
+
+We run a XenForo instance at **[forums.devanooga.com](https://forums.devanooga.com/)** for longer-form discussion that doesn’t fit in a Slack channel: project show-and-tells, job postings worth keeping searchable, technical write-ups, community planning.
+
+## Signing up
+
+Forum registration is gated by an invite code we rotate in Slack so we can keep spam down. To get it:
+
+1. [Join our Slack](/slack/) if you haven’t already.
+2. Open the **`#devanooga-meta`** channel. The current registration code is posted in the channel topic.
+
+Already registered? Head straight to **[forums.devanooga.com](https://forums.devanooga.com/)**.