Add other backup destinations

[kristianfreeman]

request for backblaze b2 here: https://twitter.com/temporalhabit/status/1235934631142338560

should be easy to manage this (the functions are set up so it just takes a filename as input)

[Stvad]

My vote is for (in the order of preference):

• GitHub/git in general (bonus points for unpacking archive, & normalizing the JSON to easily see diffs between backups)
• Dropbox
• GDrive

[Stvad]

Re github support: https://github.com/elstudio/actions-js-build/tree/master/commit has a template for the WF required.
Though I imagine people would want to do this based on their private repositories, which makes original setup a bit more complicated (though probably it's more then offset by not requiring you to do S3 setup).

Also would be awesome to run https://github.com/houshuang/note-link-janitor for markdown export. In fact let me create a separate issues for that