docs(self-hosted): provide a note for air-gapped installation (#13357)

Closes getsentry/self-hosted#3644

Author: aldy505

develop-docs/self-hosted/index.mdx

@@ -73,6 +73,10 @@ Thirty (30) day retention. No marketing. Privacy policy at sentry.io/privacy.
 
 Starting with the 22.10.0 release, we will require those running the Sentry installer to choose to opt in or out. If you are running the installer under automation, you may want to set `REPORT_SELF_HOSTED_ISSUES` or pass `--(no-)report-self-hosted-issues` to the installer accordingly.
 
+### Air-gapped installation
+
+Sentry can run in air-gapped environments, where there are no internet access. Depending on how air-tight your environment is, the best way to do so is to do installation and upgrades behind a proxy, see [Installing Behind a Proxy](#installing-behind-a-proxy) below. If it's not possible, you may build the entire Docker Compose stack on another machine, use `docker commit` to "freeze" the images, then use combination of `docker save` and `docker load` which convert the image as a `.tar` file and transfer it into the air-gapped machine. Then, you can use `docker-compose up` to start the services. Although this may seem possible, we don't provide any further help for this use case, as it's not a common scenario.
+
 ### Self-hosted Beacon
 
 If you opt-in to it, self-hosted Sentry will periodically communicate with a remote beacon server. This is utilized for a couple of things, primarily: