Move code rendering to the backend & frontend improvements (#176)

Added Chroma & Goldmark

Added Mermaidjs

More languages supported

Add default values for gist links input

Added copy code from markdown blocks

templates/base/gist_footer.html

@@ -4,6 +4,7 @@
 {{ end }}
 
 {{ define "gist_footer" }}
+
 </main>
 </div>
 {{ end }}