Add issue template link to IRLO

Author: jonas-schievink

.github/ISSUE_TEMPLATE/config.yml

@@ -3,3 +3,6 @@ contact_links:
   - name: Rust Programming Language Forum
     url: https://users.rust-lang.org
     about: Please ask and answer questions about Rust here.
+  - name: Rust Internals Forum
+    url: https://internals.rust-lang.org/
+    about: Please discuss language feature requests here.