How to upload a label config file

[TomLipshits5]

How to reproduce the behaviour

[david-engelmann]

My current pull request to accomplish: https://github.com/doccano/doccano-client/pull/63

Depending on the project type you can use a particular group of endpoints. Look for functions with span_type for SequenceLabeling, category_type for DocumentClassification or relation_type. If you want to upload a config file use the functions post_span_type_upload, post_category_type_upload or post_relation_type_upload.