Add documentation for proxying

doc/FAQ.md

@@ -65,6 +65,26 @@ only to HTTP requests.
 You can use [Let's Encrypt](https://letsencrypt.org/) to get an SSL certificate
 for free.
 
+## How do I access web services?
+code-server is capable of proxying to any port using either a subdomain or a
+subpath.
+
+### Sub-domains
+Set up a wildcard certificate for your domain and a wildcard DNS entry (or you
+can configure each subdomain individually for the ports you expect to use).
+
+Start code-server with the `--proxy-domain` flag set to your domain.
+
+```
+code-server --proxy-domain coder.com
+```
+
+Now you can browse to `<port>.coder.com`. Note that this uses the host header so
+ensure your reverse proxy forwards that information if you are using one.
+
+### Sub-paths
+Just browse to `/proxy/<port>`.
+
 ## x86 releases?
 
 node has dropped support for x86 and so we decided to as well. See