fix install docs (#422)

Change install docs to point to Github Container Registry instead of
Dockerhub

docs/root/install.md

@@ -13,12 +13,20 @@ Note that you should _never_ run with this quickstart configuration in productio
 ### To run confidant in Docker
 
 It's necessary to export your configuration variables before running confidant.
-You can either specify them as multiple -e options, or you can put them into an
+You can either specify them as multiple -e options, or you can put them into
 an environment file and use --env-file.
 
+A production-ready docker image is available in
+[GitHub Container Registry](https://github.com/lyft/confidant/pkgs/container/confidant).
+
+```bash
+docker pull ghcr.io/lyft/confidant:master
+```
+
+This image can then be ran with any of your desired command line flags:
+
 ```bash
-docker pull lyft/confidant
-docker run --env-file my_config -t lyft/confidant
+docker run --rm ghcr.io/lyft/confidant:master --help
 ```
 
 ### To build the image