rss2json requires api key for frequent calls

[claren]

The $medium_url assignment in display-medium-posts.php needs to have an api key appended to it, or rss2json.com will reject multiple calls.

Example:

$medium_url = "https://api.rss2json.com/v1/api.json?rss_url=https://medium.com/feed/" . $handle ."&api_key=XXXX";