doc: Improve docker example to mount in $HOME for easy config access

I'm surprised no one has asked any questions about this.

doc/install.md

@@ -174,7 +174,13 @@ code-server
 # It will also mount your current directory into the container as `/home/coder/project`
 # and forward your UID/GID so that all file system operations occur as your user outside
 # the container.
+#
+# Your $HOME/.config is mounted at $HOME/.config within the container to ensure you can
+# easily access/modify your code-server config in $HOME/.config/code-server/config.json
+# outside the container.
+mkdir -p ~/.config
 docker run -it -p 127.0.0.1:8080:8080 \
+  -v "$HOME/.config:/home/coder/.config" \
   -v "$PWD:/home/coder/project" \
   -u "$(id -u):$(id -g)" \
   codercom/code-server:latest