v2, add sections and reference to systemd-docker

Setup-bitwarden_rs-as-a-systemd-service.md

@@ -1,3 +1,5 @@
+These instructions require you to have compiled the bitwarden_rs binary. If you generated a docker image, you may want to look at [[Running with systemd-docker | Running-with-systemd-docker]]
+## Setup
 Making bitwarden_rs start on system startup and use the other facilities of systemd (e.g. isolation, logging,...) requires a `.service` file. The following is a usable starting point:
 ```
 [Unit]
@@ -36,8 +38,8 @@ To make systemd aware of it, run
 ```
 $ sudo systemctl daemon-reload
 ```
-
-To start this new "service", run
+## Usage
+To start this "service", run
 ```
 $ sudo systemctl start bitwarden_rs.service
 ```