[DL+] improve jingle handling

[hairmare]

Jingles are being sent as follows:

DAB+ Audio Companion URL: http://dab.example.org:8080/api/setDLS data: {'artist': 'Jetzt RaBe Mitglied werden!', 'title': 'Du losisch z Klangbecki uf RaBe 2021_3'}

• check how to recognize jingles
• decide how to handle jingles (ignore or annotate)
• decide what content types to use for jingles
• add jingle specific DL+

[hairmare]

i minimal length cutoff for tracks we DL+ on would solve this and might be the proper way to go anyway

[hairmare]

like the one i'm introducing with the linked PR

i'm keeping this issue open since i want to ensure that jingles longer than 5 seconds get displayed as the current show and not as their actual metadata anyway