Meta: provide better translation resources + improve translation workflow

[rsek]

What I mean here is providing resources to reduce the technical knowledge requirement of translation.

• Provide ready-made JSON with clear, consistent labelling + mappings (we use a lot of Document#system properties, and Babele doesn't export these automatically): Automatically generate i18n templates for compendia #602
  • i might separate this into its own repo in order to solicit feedback on the format
• update the wiki to reflect the above
• add links to existing translation projects in README
• consider a template module repo that people can use to get started?
  • alternatively: centralize all translations to this repo? (wouldn't be my first choice, as managing that sounds like a lot of work! but maybe there's some benefits to keeping all the localization data in one place)
• trawl r20's ironsworn translation data and crib useful strings from it
• investigate means of entering translation data that don't require someone to be familiar with JSON/github