README: smalltalk syntax highlighting

README.md

@@ -36,7 +36,9 @@ The main message there is ``<<``, the high-level message to put an object on a s
 
 With
 
-     Silk new << 'Hello, world!'
+```smalltalk
+Silk new << 'Hello, world!'
+```
 
 you append a text node to the body.
 
@@ -44,17 +46,21 @@ Silk uses the browser support for ``querySelector`` to get to the elements - tha
 
 For example with
 
-    '#log' asSilk << 'another item'
+```smalltalk
+'#log' asSilk << 'another item'
+```
 
 you append the text ``another item`` to the element with id ``#log``.
 
 Silk uses DNU (Smalltalk ``does not understand``) to help you to create HTML elements, and uses associations as a way to set attributes. So you do:
 
-     Silk new
-        H1: {'id'->'header'. 'Welcome'};
-        P: {'id'->'welcome'. 'This is an acme page.'. 'It was created by Silk'};
-        HR;
-        SMALL: {'id'->'footer'. 'We do not guarantee anything.'}
+```smalltalk
+Silk new
+   H1: {'id'->'header'. 'Welcome'};
+   P: {'id'->'welcome'. 'This is an acme page.'. 'It was created by Silk'};
+   HR;
+   SMALL: {'id'->'footer'. 'We do not guarantee anything.'}
+```
 
 BTW, `foo H1: bar` is just a convenience for `foo H1 << bar; yourself`.