Escape new lines from JSON-ld data

[tcitworld]

The JSON-ld data does not escape newlines, leading to broken data (as JSON does not allow this).

For instance with this event:

<script type="application/ld+json">
    {
      "@context": "http://schema.org",
      "@type": "Event",
      "url": "https://gettogether.community/events/34457/freak-stammtisch/",
      "name": "FRe;AK Stammtisch",
      "description": "Einstmals das Treffen der Friendica und Hubzilla Nutzerïnnen aus Berlin und Umgebung. Heute ein munteres Zusammenkommen von Fedizen unabhängig vom der Fediverse Plattform die verwendet wird.

Wir treffen uns in der [c-base](https://c-base.org) - Rungestrasse 20
10179 Berlin.",
      "image": "https://gettogether.community/media/CACHE/images/team_covers/freaks-berlin_fu3bIBO/24d96daa25f309fbc976d6f54e5da3d3.png",
      "organizer": {
          "@type": "Organization",
          "name": "FRe;AK",
          "url": "https://gettogether.community/freaks/"
      },
      
      "location": {
        "@type": "Place",
        "name": "c-base",
        "address": "Rungestraße 20, 10179 Berlin, Germany"
      },
      
      "startDate": "2023-07-03T17:00:00+00:00",
      "endDate": "2023-07-03T20:00:00+00:00"
    }
</script>

Some kind of filter here should be enough:

GetTogether/get_together/templates/get_together/events/show_event.html

Line 18 in 6708944

"description": "{{event.summary}}",