Update readme.txt for WordPress 5.6 support.
Check that a widget exists on the current page before trying to render the checkin map.
Always query the 4Sq API on page load to work around cases where the short code (with no widgets) is being used.
Remove support for private checkins; this was never properly implemented and now the 4Sq API doesn't support filtering these out (if it ever did)
Up the version number to v1.3.0; there's sufficient changes since v1.2.0 to warrant a minor version increment.