Add documentation for routes (#2496)

* Add documentation for routes

* Rename exit-node to routes and add redirects
* Add a new section on subnet routers
* Extend the existing exit-node documentation
* Describe auto approvers for subnet routers and exit nodes
* Provide ACL examples for subnet routers and exit nodes
* Describe HA and its current limitations
* Add a troubleshooting section with IP forwarding

* Update features page for 0.26

Add auto approvers and link to our documentation if available.

* Prefer the console lexer when commandline and output mixed

docs/ref/dns.md

@@ -76,14 +76,14 @@ hostname and port combination "http://hostname-in-magic-dns.myvpn.example.com:30
 
     === "Query with dig"
 
-        ```shell
+        ```console
         dig +short grafana.myvpn.example.com
         100.64.0.3
         ```
 
     === "Query with drill"
 
-        ```shell
+        ```console
         drill -Q grafana.myvpn.example.com
         100.64.0.3
         ```