Added subsection for multiple language CSV column names

[ekansa]

brief description of changes

Responds to a gap in documentation identified by @chiatt where we lacked instruction on how to structure CSV files to import business data that contain string nodes in multiple languages.

issues addressed

https://github.com/archesproject/arches/issues/9288#issuecomment-1513028942

further comments

The updated section is demoed here: https://arches.readthedocs.io/en/csv_int_7_3/localizing-arches/#csv-column-field-names-indicating-languages

Once approved, I'll update all version 7 branches to include this update.

This box must be checked

• [x] the PR branch was originally made from the base branch

This box should be checked

• [x] after these changes the docs build locally without error

This box should only be checked you intend to follow through on it (we can do it on our end too)

• [x] I will cherry-pick all commits in this PR into other branches that should have them after this PR is merged