adding license metadata to our packages

[edublancas]

see: ploomber/core#54 for context.

I noticed some of our packages are still missing license metadata

https://github.com/ploomber/sklearn-evaluation/blob/master/setup.py
https://github.com/ploomber/ploomber-engine/blob/main/setup.py

(there might be more, we need to check jupysql)

[edublancas]

example of how to fix it: https://github.com/ploomber/core/blob/f81a4ce8f4d8b9e3dbc1b5a4a630ddc072ad884c/setup.py#L43

[tl3119]

Here is the PR for ploomber-engine: ploomber/ploomber-engine#80
Sklearn-evaluation is blocked by the last PR
Jupysql already has the license metadata

[edublancas]

great work @tl3119 !