Enable highlighting for blame

Fixes #3675
Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

app/views/projects/blame/show.html.haml

@@ -8,7 +8,7 @@
         = @path
         %small= number_to_human_size @blob.size
       %span.options= render "projects/blob/actions"
-    .file-content.blame
+    .file-content.blame.highlight
       %table
         - current_line = 1
         - @blame.each do |commit, lines|
@@ -33,6 +33,7 @@
                     - current_line += 1
             %td.lines
               %pre
+                %code{ class: highlightjs_class(@blob.name) }
                   :erb
                     <% lines.each do |line| %>
                       <%= line %>