A simple feed file that follows the 1.0 spec of the JSON Feed standard established by Manton Reece and Brent Simmons.
Copy the feed.json file to the root directory of your Jekyll install.
Add the following line to your head.html (or similar theme file where the <head> section of your site is defined.
<link rel="alternate" title="{{ site.title }}" type="application/json" href="{{ "/feed.json" | absolute_url }}" />
If your server is not configured to serve JSON files, you might need to add this to your .htaccess file:
AddType application/json .json