Update README.md

Fix code block formatting

README.md

@@ -5,26 +5,26 @@ A Racket package for creating macros with built-in support for defining sub-macr
 
 Sometimes complex Racket macros need a way for their syntax to be extended. The Racket match form is an example, new patterns can be created for match using define-match-expander. This racket package provides a form for defining a macro with the ability to define expanders for the macro. Consider this contrived example:
 
-(define-syntax call-each
+    (define-syntax call-each
       (syntax-parser
         [(_ f (expr ...))
         #'(begin (f expr) ...)]))
         
-(call-each displayln (1 2 3))
+    (call-each displayln (1 2 3))
 
 If a user of this macro wished for a way to specify a range of numbers as the arguments, the user must define their own version of call-each with support for ranges that expands to using the original call-each. However, this racket package provides a form, define-syntax-with-expanders:
 
-(define-syntax-with-expanders call-each
+    (define-syntax-with-expanders call-each
       (syntax-parser
         [(_ f (expr ...))
         #'(begin (f expr) ... )]))
     
-(define-call-each-expander foo
+    (define-call-each-expander foo
       (syntax-parser
         [(_ low:number high:number)
         #`(#,@(range (syntax-e #'low) (syntax-e #'high)))]))
         
-(call-each displayln (foo 1 4))
+    (call-each displayln (foo 1 4))
 
 The define-syntax-with-expanders form creates a define-call-each-expander form, which defines syntax transformers that are only used inside the body of a call-each form and expand before call-each does.