add adr for how meta-schemas and dialects work under a stable specification#1406

gregsdennis wants to merge 2 commits intomainjson-schema-org/json-schema-spec:mainfrom

gregsdennis/adr-open-vs-closed-meta-schemasjson-schema-org/json-schema-spec:gregsdennis/adr-open-vs-closed-meta-schemasCopy head branch name to clipboard