Support customization of the header [with fix]

Thanks for building such an awesome plugin, it just saved me hours of fiddling with regex! Just a simple request that would make this perfect – could you apply filter to the header so that:

1. It’s possible to maintainably change the label (i.e. from “Notes:” to “Sources:”)
2. Translation is possible

In the version I’m using, I changed line 84 from:
$content .= '<div class="simple-footnotes"><p class="notes">Notes:</p><ol>';
to
$content .= apply_filters('simple_footnotes_header','<div class="simple-footnotes"><p class="notes">Notes:</p><ol>');

I’ve set up a filter in my functions.php file with a custom string, including a gettext target:

function footnote_header($header){
	return sprintf(
		'<div class="simple-footnotes"><h2>%s:</h2><ol>',
		__('Sources','theme')
		);
}
add_filter('simple_footnotes_header','footnote_header');

This is working perfectly for me. Could you add the filter to your plugin?

https://www.ads-software.com/extend/plugins/simple-footnotes/