docs(pro): add local group concurrency section (#2551)

docs/gitbook/SUMMARY.md

@@ -83,6 +83,7 @@
 * [Groups](bullmq-pro/groups/README.md)
   * [Rate limiting](bullmq-pro/groups/rate-limiting.md)
   * [Concurrency](bullmq-pro/groups/concurrency.md)
+  * [Local group concurrency](bullmq-pro/groups/local-group-concurrency.md)
   * [Max group size](bullmq-pro/groups/max-group-size.md)
   * [Pausing groups](bullmq-pro/groups/pausing-groups.md)
   * [Prioritized intra-groups](bullmq-pro/groups/prioritized.md)

docs/gitbook/bullmq-pro/groups/local-group-concurrency.md

@@ -0,0 +1,21 @@
+# Local group concurrency
+
+It is also possible to set a specific concurrency value to a given group. This is useful if you require that different groups should run with different concurrency factors.
+
+Please keep in mind that when specifying a group's concurrency factor, you are storing this value in Redis, so it is your responsibility to remove it if you are not using it anymore.
+
+You can use the `setGroupConcurrency` method like this:
+
+```typescript
+import { QueuePro } from '@taskforcesh/bullmq-pro';
+
+const queue = new QueuePro('myQueue', { connection });
+const groupId = 'my group';
+await queue.setGroupConcurrency(groupId, 4);
+```
+
+And you can use the `getGroupConcurrency` method like this:
+
+```typescript
+const concurrency = await queue.getGroupConcurrency(groupId);
+```