Works: Add 377 for language

[jenniferward]

Please add 377$a for language in Works. It should go somewhere in the "Main entry fields" section. 377 should be repeatable. https://www.loc.gov/marc/authority/ad377.html

I think it can be styled like 041 in Sources, so label Language code and include the drop-down list of languages there.

In MARC, 130$l records language as part of the title (https://www.loc.gov/marc/authority/ad130.html), but that field is a free-text field and can be formatted like Italian & Sanskrit. It would be better to use our codes in 377 for now.