Make the content of the Bento file more version control-friendly

[Hermholtz]

Right now all slides are stored basically in a single very long line, as follows:

    <script type="application/bento+json" id="bento-doc">
{"$schema":"https://bento.page/schema/slides.json","format":"bento/slides","version":1,"docId":" ........ "slides": [ {...} ] ....
    </script>

Please change it so that every slide is in a different line:

"slides":[
{"id":"slide-xx1", .... },
{"id":"slide-xx2", .... },
...
],

This way it'll be much easier to use Git to spot differences between versions - a change on one line will mean this slide was changed, and added/deleted slides will be also shown nicely.

Right now it's hard to use Git to spot differences between two commits, or a commit and a current change. A line is almost 3 million characters, and VSCode is choking when I'm trying to compare two versions.

Thanks in advance!