Include Docker installation reference in separate-server.md (#304)

* Include Docker installation reference in separate-server.md

Added import statement for Docker installation instructions.

* Update docs/install/subscription-page/separate-server.md

Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>

---------

Co-authored-by: Yury Kastov <kastov@gog.sh>
Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>

Author: 3 people

docs/install/subscription-page/separate-server.md

@@ -45,6 +45,8 @@ Make sure you have Docker installed on the server where you will install the sub
 
 :::
 
+import InstallDocker from '/docs/partials/\_install_docker.md';
+
 ```bash title="Creating docker-compose.yml file"
 mkdir -p /opt/remnawave/subscription && cd /opt/remnawave/subscription && nano docker-compose.yml
 ```