html: Improve block rendering

org/testdata/example.org

@@ -51,6 +51,25 @@ this one is cheating a little as tags are ALWAYS printed right aligned to a give
   2. regular link [[https://example.com][example.com]] link with description
   3. regular link to a file (image) [[file:my-img.png]]
   4. auto link, i.e. not inside =\[[square brackets]\]= https://www.example.com
+** blocks
+#+BEGIN_SRC bash
+echo a bash source block
+#+END_SRC
+
+#+BEGIN_SRC
+a source block without a language
+and a second line
+and a third one
+#+END_SRC
+
+#+BEGIN_EXAMPLE foo bar baz
+an example block
+with multiple lines
+#+END_EXAMPLE
+
+#+BEGIN_QUOTE
+Mongodb is very webscale
+#+END_QUOTE
 ** Footnotes
 - normal footnote reference [fn:1]
 - further references to the same footnote should not [fn:1] render duplicates in the footnote list