Improve code language detection for ERB and HTML

This improves language detection for code examples that include ERB or
HTML tags in a trailing position, such as `Title: <%= @post.title %>`.

Author: jonathanhefner

lib/sdoc/postprocessor.rb

@@ -130,7 +130,7 @@ def guess_code_language(code)
       else
         "yaml"
       end
-    when /^ *<[%a-z]/i
+    when /^ *<[%a-z]|%>$|<\/\w+>$/i
       "erb" # also highlights HTML
     else
       "ruby"

spec/postprocessor_spec.rb

@@ -400,6 +400,10 @@
         <%= 1 + 1 %>
       ERB
 
+      _(SDoc::Postprocessor.guess_code_language(<<~ERB)).must_equal "erb"
+        1 + 1 = <%= 1 + 1 %>
+      ERB
+
       _(SDoc::Postprocessor.guess_code_language(<<~ERB)).must_equal "erb"
         <% x = 1 + 1 %>
       ERB
@@ -413,6 +417,10 @@
       _(SDoc::Postprocessor.guess_code_language(<<~HTML)).must_equal "erb"
         <p>1 + 1 = 2</p>
       HTML
+
+      _(SDoc::Postprocessor.guess_code_language(<<~HTML)).must_equal "erb"
+        1 + 1 = <span>2</span>
+      HTML
     end
 
     it "guesses erb for HTML that includes ERB" do
@@ -432,6 +440,11 @@
         Object.new # => #<Object>
       RUBY
 
+      _(SDoc::Postprocessor.guess_code_language(<<~RUBY)).must_equal "ruby"
+        Pathname("/span")
+        # => #<Pathname:/span>
+      RUBY
+
       _(SDoc::Postprocessor.guess_code_language(<<~RUBY)).must_equal "ruby"
         image_tag("image.png")
         # => <img src="/assets/image.png" />