Rename QuestionAnswering template to QuestionAnsweringExtractive

[lewtun]

Following the discussion with @thomwolf in #2255, this PR renames the QA template to distinguish extractive vs abstractive QA. The abstractive template will be added in a future PR.

[lhoestq]

I like having "extractive" in the name to make things explicit. However this creates an inconsistency with transformers.

See
https://huggingface.co/transformers/task_summary.html#extractive-question-answering

But this is minor IMO and I'm ok with this renaming

[lewtun]

I like having "extractive" in the name to make things explicit. However this creates an inconsistency with transformers.

See
https://huggingface.co/transformers/task_summary.html#extractive-question-answering

But this is minor IMO and I'm ok with this renaming

yes i chose this convention because it allows us to match the QuestionAnsweringXxx naming and i think it's better to have task_name-subtask_name should auto-complete ever become part of the Hub :)