Allow several tags sets
Closing since we don't need to update the tags of those three datasets (for each one of them there is only one tag set)
Hi !

Currently we have three dataset cards : snli, cnn_dailymail and allocine.
For each one of those datasets a set of tag is defined. The set of tags contains fields like `multilinguality`, `task_ids`, `licenses` etc.

For certain datasets like `glue` for example, there exist several configurations: `sst2`, `mnli` etc. Therefore we should define one set of tags per configuration. However the current format used for tags only supports one set of tags per dataset.

In this PR I propose a simple change in the yaml format used for tags to allow for several sets of tags.

Let me know what you think, especially @julien-c let me know if it's good for you since it's going to be parsed by moon-landing