Add some 'sane' github labels

[damianhorna]

Like here: https://medium.com/@dave_lunny/sane-github-labels-c5d2e6004b63

It would be also cool if we add a label named "task" or something like this in order to indicate just a regular task that needs to be done, so that our project meets our expectations. This is not necessarily an enhancement though, but just one of our goals we envisioned when planning the library.