Enable `Style/BlockDelimiters` rule.

.rubocop.yml

@@ -2,11 +2,11 @@ AllCops:
   TargetRubyVersion: 2.4
   DisabledByDefault: true
   Exclude:
-    - 'db/schema.rb'
-    - 'bundle/**/*'
-    - 'vendor/**/*'
-    - 'node_modules/**/*'
-    - 'public/**/*'
+    - "db/schema.rb"
+    - "bundle/**/*"
+    - "vendor/**/*"
+    - "node_modules/**/*"
+    - "public/**/*"
 
 # Prefer &&/|| over and/or.
 Style/AndOr:
@@ -17,6 +17,10 @@ Style/AndOr:
 Style/BracesAroundHashParameters:
   Enabled: true
 
+# Check for uses of braces or do/end around single line or multi-line blocks.
+Style/BlockDelimiters:
+  Enabled: true
+
 # Align `when` with `case`.
 Layout/CaseIndentation:
   Enabled: true