Document way to do notice compatibility routes with Nginx reverse-proxy instead

installation/pleroma.nginx

@@ -81,6 +81,19 @@ server {
         proxy_pass http://phoenix;
     }
 
+    # Uncomment this if you want notice compatibility routes for frontends like Soapbox.
+    # location ~ /@.+/([^/]+) {
+    #     proxy_pass http://phoenix/notice/$1;
+    # }
+    #
+    # location ~ /@.+/posts/([^/]+) {
+    #     proxy_pass http://phoenix/notice/$1;
+    # }
+    #
+    # location ~ /.+/status/([^/]+) {
+    #     proxy_pass http://phoenix/notice/$1;
+    # }
+
     location ~ ^/(media|proxy) {
         proxy_cache        pleroma_media_cache;
         slice              1m;