Adds files to the project as added by PM.

Adds files to the project as added by PM. The files have to be uploaded beforehand (see "POST /v2/projects/{projectId}/files/upload" operation). The following properties can be specified for each file:<ul><li>category (required, 400 Bad Request is returned otherwise)</li><li>languageIds – when the file category depends on a list of languages</li><li>languageCombinationIds – when the file category depends on a list of language combinations</li></ul>