Update README.md (#568)

Standardizes the codeblocks (noticed one was missing a language tag).

docs/README.md

@@ -87,12 +87,14 @@ It's often desirable to have a client that'll be used for inserting jobs, but
 not working them. This is possible by omitting the `Queues` configuration, and
 skipping the call to `Start`:
 
-	riverClient, err := river.NewClient(riverpgxv5.New(dbPool), &river.Config{
-	    Workers: workers,
-	})
-	if err != nil {
-	    panic(err)
-	}
+```go
+riverClient, err := river.NewClient(riverpgxv5.New(dbPool), &river.Config{
+    Workers: workers,
+})
+if err != nil {
+    panic(err)
+}
+```
 
 `Workers` can also be omitted, but it's better to include it so River can check
 that inserted job kinds have a worker that can run them.