modify in_language attribute to include multiple languages

[ddooley]

Is your feature request related to a problem? Please describe.
We are creating a multilingual LinkML schema add-on. In LinkML metadata spec, the in_language only allows one locale to be stated, such as 'en' or 'en_US', but we would like this to accommodate a list or array of locales, for use in our DataHarmonizer tool.

Describe the solution you'd like
Currently LinkML enables an overall in_language attribute on the schema to indicate language being used in title, descriptions, comment attribute fields of classes, slots and enumerations. We'd like a slight expansion of this so that a schema can mention more than one language:

The first language mentioned would be pertinent to the schema yaml file itself, while the remaining languages would indicate alternate language resources are available for the schema. In our case we plan to have them located in a folder structure like so:

Schema Locale alternates can be in yaml, but also in our case for browser loading, we have a schema.json version. This file will have language locale entries for all translated titles, descriptions, examples, comments etc. For example a portion of a French schema version, showing a slot's key language attributes (via Google Translate so pardon if a bit off) which can be overlayed into an application presentation layer:

How important is this feature? Select from the options below:
• Medium - can do work without it; but it's important (e.g. to save time or for convenience)