Export sheets as file

[kuroidoruido]

The goal here is to create an export button to keep offline the state of one character sheet or multiple character sheet.

We can discuss about this, but in my mind I see an export button on the sheet selector page, under the "My Sheets" tab, to export all characters, or selecting some characters. When we select characters we want to export, I think we need to add a checkbox (or something like that) beside the character name badge, not the sheet card because we will have in the future the ability to keep multiple characters for each sheet.

Again we can discuss about this, but I have in mind the exported file should be a simple json file, named <export_date>_.vrpg.json

Example:

• 2020-09-23_full.vrpg.json => for full export
• 2020-09-23_Adam-Ocalan.vrpg.json => when export only the character Adam Ocalan
• 2020-09-23_characters.vrpg.json => when export multiple characters

[Fleker]

I can start work on this endeavor, but will probably split into a few separate PRs to incrementally add exporting capability (and then importing back in)