Add screenshoter

I think it's would be useful.
It's capture image from the webView widget, uploads it on imgur and copy to clipboard direct link to uploaded file. I checked it on my Arch linux and it builds and working fine.
My C++ and Qt knowledge is very low so code may (should) contain some mistakes. Any comment and fixes are welcome.
According to me, yes, but that's just me. Long lines are harder to read, and that feels like an unnecessary waste of a character with no increase in readability, even if it's just a single column.