add a button to collapse PR overview description or to jump to comments/change files section

as a PR reviewer , i want to quickly jump to comments section so i can quickly review them,
now if i have long description ( which could be genereated by merging two major feature branches ) , i have to scroll down all the way till the overview description ends, then i can start seeing comments and changed files.

I think we should add a button to collapse overview description area, so that user can quickly jump to comment/ changed files and do the real work :smiley: