fix(rss): set srt transcripts' mimetype to application/x-subrip with rel="captions" attribute

closes #360

app/Config/Mimes.php

@@ -276,7 +276,7 @@ class Mimes
         ],
         'svg' => ['image/svg+xml', 'image/svg', 'application/xml', 'text/xml'],
         'vcf' => 'text/x-vcard',
-        'srt' => ['text/srt', 'text/plain', 'application/octet-stream'],
+        'srt' => ['application/x-subrip', 'text/srt', 'text/plain', 'application/octet-stream'],
         'vtt' => ['text/vtt', 'text/plain'],
         'ico' => ['image/x-icon', 'image/x-ico', 'image/vnd.microsoft.icon'],
         'stl' => ['application/sla', 'application/vnd.ms-pki.stl', 'application/x-navistyle'],

app/Helpers/rss_helper.php

@@ -360,6 +360,9 @@ if (! function_exists('get_rss_feed')) {
                         pathinfo($episode->transcript->file_url, PATHINFO_EXTENSION)
                     ) ?? 'text/html',
                 );
+                // Castopod only allows for captions (SubRip files)
+                $transcriptElement->addAttribute('rel', 'captions');
+                // TODO: allow for multiple languages
                 $transcriptElement->addAttribute('language', $podcast->language_code);
             }