Include git clone command in "Clone or download" section #2121

I'm usually copying the URL of my repos just to do git clone [paste] && cd [type-name-here]. I'd find it very useful to have that command right at my fingertips in GitHub.

This is basically what was suggested in #1355, but instead of modifying the existing behavior, I would include the command as an additional option:

<img alt="Prototype of the desired functionality (screenshot)" src="https://user-images.githubusercontent.com/1922624/58941343-dbcec880-877b-11e9-9045-d8813736a473.png" width="380">

I think this change would be subtle/unobtrusive, but it would be interesting to get maintainer/community feedback on whether this a more widely requested feature or it's just me. 🙂

If this proposal gets any approval, I'd be happy to implement it.