create stable URIs for json schemas at citationstyle.org

Perhaps as a separate change in the future, I wonder if it makes sense to define a URL like csl-data-schema.citationstyles.org that can be changed for $id and can be updated if the source code path or repo changes.

I think @dstillman was recommending something like this, though I think he was recommending hosting a copy of the schema files on that site.

Is it feasible for us to do both changes together? That would ensure only one breaking change, rather than two.

If we do, do we need to version the json schema URI ids?

I don’t know know who maintains that site, though, or how!

_Originally posted by @bdarcus and responding to @dhimmel in https://github.com/citation-style-language/schema/pull/212#issuecomment-636482128_

[rmzelle]

“resource”? E.g. “http://resource.citationstyles.org/schema/”.

[dstillman]

I would do singular schema.

But it’s worth thinking whether there are other resources CSL might want to make available in a permanent (i.e., redirectable) manner.