Add Kruskal's algorithm for minimal spanning tree

[maurobringolf]

This repo is really cool and I would like to contribute 🎉 . I added an implementation of Kruskal's MST algorithm and one of the examples from Wikipedia as test case. I tried to mimic the module style of existing algorithms, let me know if I should change the structure or if anything else is missing.

I am not sure how to add documentation for the website, but am willing to help with it if you tell me what to do.

[mgechev]

@maurobringolf will add a reminder to update the list of contributors soon.

[maurobringolf]

@mgechev So cool, thank you! I will look into more algorithms to add/improve.