Use Markdown for Profiles Collection

[ghost]

Currently a Profiles Jekyll collection is used to create and manage profiles. Those files contain YAML front matter and are currently suffixed with an html extension. The presence of an html extension can trip up code editors like Atom as the editor will not properly parse and interpret front matter in an HTML document.

Moving to a md or markdown file extension helps mitigate this problem, affords a better developer experience, provides backwards compatibility, enables support for certain Jekyll cloud editors, such as Siteleaf; and enables highlighting, completions and keyboard shortcuts for supporting editors.

Unless there are any concerns, I will create a pull which will change the default file extension to md to resolve this issue.

Related issues:
jekyll/jekyll#1654

[eduardoboucas]

I honestly can't remember why I decided to use HTML. But yes, if switching to Markdown doesn't cause any issues, I'm more than happy to see that changed.