Add #dendrite-dev to the README
I suspect this is why we're getting a lot of people coming in to #dendrite asking dev-related questions.
@@ -18,6 +18,8 @@ We aim to try and make it as easy as possible to jump in.
For questions about Dendrite we have a dedicated room on Matrix
[#dendrite:matrix.org](https://matrix.to/#/#dendrite:matrix.org).
+Development discussion should happen in
+[#dendrite-dev:matrix.org](https://matrix.to/#/#dendrite-dev:matrix.org).
# Progress
