Add table_exists method to Catalog

[anupam-saini]

Closes#507

[Fokko]

This looks good @anupam-saini, thanks for working on this. One more request, could you also update the docs? Otherwise people won't be able to find this :)

[anupam-saini]

This looks good @anupam-saini, thanks for working on this. One more request, could you also update the docs? Otherwise people won't be able to find this :)

Good point :)

[Fokko]

Thanks @anupam-saini for working on this 🚀 and thank @syun64 for the review!