Markdownify description and show link only when isset

[i-sanyam]

In list.html

if description is not set in params of the blog .md file, then trimmed raw content is displayed. The trimmed raw content is in markdown and can have special characters that will then show unformatted in the description. Thus adding a pipe operator and mardownifyto fix it.

In single.html

in the blog post, show the link only when link is set in params in .md blog file.