Add solargraph in development, document usage with bundled gems

README.md

@@ -23,7 +23,6 @@ so:
 
 After these steps, you should have a working Rails app with a handful of test
 users running on [http://localhost:3000](http://localhost:3000).
-
 Log in with username "admin" and password "admin is admin". All users listed on
 [http://localhost:3000/admin/ldap_users](http://localhost:3000/admin/ldap_users)
 have the password "user is user".
@@ -79,6 +78,15 @@ The setup task will first delete any existing entries in the directory tree
 Note that all 389ds data is stored in `tmp/389ds`. So if you want to start over
 with a fresh installation, delete both that directory as well as the container.
 
+#### Solargraph
+
+[Solargraph](https://solargraph.org/) is a Ruby language server, which you may
+use with your editor to add features like auto-completion and syntax
+validation. You can add inline documentation for bundled gems with this
+command:
+
+    bundle exec yard gems
+
 ## Documentation
 
 ### Rails