Keep elapsed time when finished

[NathanBaulch]

I'd like to keep the elapsed time visible once the progress bar finishes, just like the four example animations in the main README show. This seems to be the normal behavior in most popular CLI progressbar libraries I've found across various languages.

This change was introduced in commit 953dc78edb and released in v3.6.2. I don't mind if it's made optional, but either way the inaccurate example animations should probably be updated.

[schollz]

Would accept a PR for this