modify tqdm use

[geezacoleman]

slight variation to the use of tqdm already added from #85 . Included in all importers/exports and with a defined length for progress/time remaining estimation.

Progress bar style can be updated as per some of the examples here by changing pbar = tqdm(desc="", total=length_of_files, ascii=' ='). Colour etc. can also be changed, but maybe not so critical!

[alexheat]

Hi @geezacoleman thank you for making a contribution. Your new code has failed one of the automated tests so I want to resolve that before checking it in. You can see how to run the tests on your side here https://github.com/pylabel-project/pylabel/tree/dev/tests

[geezacoleman]

It looks like I left total=range(0, df.shape[0]) when it should just be total=df.shape[0] for setting up the progress bar in the COCO exporter. This seems to fix that error on my end.