fix: HTML5 audio not supported weirdly (#49)

This issue is actually introduced by no the controls attribute in
audio node, and Nokogiri's XML parser will cause blank value of
attribute lost.

Author: jeffreytse

lib/jekyll-spaceship/processors/media-processor.rb

@@ -178,7 +178,7 @@ def handle_audio(element, data)
         " #{cfg['loop'] ? 'loop' : ''}"\
         " src=\"#{cfg['src']}\""\
         " style=\"#{cfg['style']}\""\
-        " controls>" \
+        " controls=\"true\">" \
         "<p> Your browser doesn't support HTML5 audio."\
         " Here is a <a href=\"#{cfg['src']}\">link to download the audio</a>"\
         " instead. </p>"\