Add title attribute which leads to tooltip with contribution type

[revelt]

We should add title attributes, like original all-contributors CLI does. This way tooltips are shown explaining the contribution type:

That's extra type of contribution straight after url:

[📖](https://github.com/codsen/unescape-js/commits?author=Revelt)

needs to be changed to:

[📖](https://github.com/codsen/unescape-js/commits?author=Revelt "Documentation")

then tooltips will start to appear:

[mbad0la]

Makes sense @revelt ! Would you like to add this functionality?
We don't maintain this plugin, so we miss out on any new spec addition to all-contributors 😞

[revelt]

Feel free to assign to me. I can also help to maintain this project.