Add markdown linting support

manuscript/recipes/realms.md

@@ -32,12 +32,13 @@ Features include:
 
 Since we'll start with a basic Realms install, let's just create a single directory to hold the realms (SQLite) data:
 
-```
+```bash
 mkdir /var/data/realms/
 ```
 
 Create realms.env, and populate with the following variables (_if you intend to use an [oauth_proxy](/reference/oauth_proxy) to double-secure your installation, which I recommend_)
-```
+
+```bash
 OAUTH2_PROXY_CLIENT_ID=
 OAUTH2_PROXY_CLIENT_SECRET=
 OAUTH2_PROXY_COOKIE_SECRET=
@@ -106,4 +107,4 @@ Log into your new instance at https://**YOUR-FQDN**, authenticate against oauth_
 [^1]: If you wanted to expose the Realms UI directly, you could remove the oauth2_proxy from the design, and move the traefik_public-related labels directly to the realms container. You'd also need to add the traefik_public network to the realms container.
 [^2]: The inclusion of Realms was due to the efforts of @gkoerk in our [Discord server](http://chat.funkypenguin.co.nz). Thanks gkoerk!
 
---8<-- "recipe-footer.md"
+--8<-- "recipe-footer.md"