[ENH] Add a pre-commit check to prevent urls pointing to pymc docs

[juanitorduz]

Fixes #292

I would support by solving this issue. However from the description I am not 100% the cope of which subfolders I need to add. I am taking the implementation from pymc-devs/pymc#5486 as suggested in the issue description.

Once I get some initial feedback I will keep working on this one :)

[OriolAbril]

Thanks! It should check all the files inside the examples/ folder except the conf.py file.

[juanitorduz]

@OriolAbril is cc4d58f enough or should add / remove websites from the entry: > specification?

[OriolAbril]

Thanks! Can you check if any of the now temporarily excluded notebooks is also in the "Done" column of the tracker project? https://github.com/pymc-devs/pymc-examples/projects/1

[juanitorduz]

Out of the 13 tickets in the "Done" column I do not see any which is also in this exclusion list.

[OriolAbril]

Out of the 13 tickets in the "Done" column I do not see any which is also in this exclusion list.

Great, thanks for the PR, I think it is ready to merge