Internationalization is broken for card method

We don't have a good internationalization story for the rendering methods spec at present.

The HTML Rendering Method is fully i18n compliant, as long as we state that the preferred language needs to be sent into the HTML environment.

It might be useful to also have a language tag on the rendering method so a client has an easier time picking between them. This is especially true for the card method, which could be greatly simplified if a language went with each template. Embedding a mixed set of language tags within the template would result in far more complicated renderers and, likely, broken UX. So, either we need to make sure that all human-displayable strings support i18n (the current card spec does not support that), or we need to be able to specify that a specific card is for a specific language. These are things that JSON-LD gave us for free, but since we are using JSON for the card inputs/outputs, we have to create a full i18n story for those objects in order to pass i18n review.

This issue is to track this concern and address it before we get i18n review.