Replace with C-Architecture

Author: samestep

src/tools/rust-analyzer/docs/dev/README.md

@@ -47,6 +47,10 @@ https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Frust-analyzer
   Each triaged issue should have one of these labels.
 * [fun](https://github.com/rust-lang/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3Afun)
   is for cool, but probably hard stuff.
+* [C-Architecture](https://github.com/rust-lang/rust-analyzer/issues?q=is%3Aissue%20state%3Aopen%20label%3AC-Architecture)
+  is for moderate/large scale architecture discussion.
+  Also a kind of fun.
+  These issues should generally include a link to a Zulip discussion thread.
 
 # Code Style & Review Process