Add Docker install instructions to abra

docs/abra/install.md

@@ -17,3 +17,17 @@ curl https://install.abra.coopcloud.tech | bash -s -- --rc
 ## Installer script source
 
 You can view that [here](https://git.coopcloud.tech/coop-cloud/abra/src/branch/main/scripts/installer/installer).
+
+## Using Docker
+
+```
+docker run \
+	-v $HOME/.abra:/.abra \
+	git.coopcloud.tech/coop-cloud/abra app ls
+```
+
+!!! note
+	If you're using symlinks, e.g. for [sharing
+	`~/.abra`](/operators/handbook/#sharing-abra), add more `-v` options for each
+	directory you're symlinking to, e.g. `-v
+	$HOME/Projects/CoopCloud/apps:/home/user/Projects/CoopCloud/apps`