Preserve the left navigation scroll position in the docs

[trav-c]

Describe the issue

When navigating to a new entry in the left nav menu the menu is reset to the top of the page every time. For example if you open the 'Available Services' category and scroll down then click on an entry, the nav menu is scrolled back to the top each time, which makes navigating the service listing somewhat frustrating.

I would suggest that ideally the navigation scroll position should just remain where it is when navigating between entries, but failing that it should at least jump to a location where the select page is visible.

Links

https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/ec2.html

[tim-finnigan]

Thanks @trav-c for this suggestion, I also think this would be a nice improvement. I'll also link a somewhat related feature request I created recently: https://github.com/boto/boto3/issues/3692. I think both the request here and in https://github.com/boto/boto3/issues/3692 would help with navigating between services/commands.