Update README with role syncing info

README.md

@@ -24,6 +24,21 @@ Note: You don't need to setup the theme in `master` realm from v0.3.0.
 3. (Optional) Set Guild Id(s) to allow federation if you want.
 
 
+### Syncing roles
+
+To sync roles from Discord -> Keycloak, do the following:
+
+1. Under the `discord` Identity Provider, fill out `Discord Roles mapping` value with the roles you want synced:
+  - The format is `Discord-Guild-ID:Discord-Role-ID:Group-Name`, like so: `613425648685547541:613426529623605268:discord-devs-moderators`
+  - You can specify multiple roles by separating them with commas: `613425648685547541:613426529623605268:discord-devs-moderators,613425648685547541:936746847437983786:discord-devs-modmail`
+2. Set up a Mapper under the `discord` Identity Provider:
+  - Set Mapper Type to `Claim to Group Mapper`
+  - Set Claim to `discord-groups`
+  - Tick Create Groups if not exists
+
+If the above doesn't get role syncing working, fiddle around with the Sync mode override. (I have mine set to `Force`, so it re-imports info on every login)
+
+
 ## Source Build
 
 Clone this repository and run `mvn package`.