That is done by a lot of people. The only problem is that water from the hose bib will be cold, and in winter, in some locations, it will be much too cold. You can have a plumber put a tee in the hot and cold water piping under a sink, with shutoff valves, or you could install a shower mixer valve the same way, same location. But, the easiest way is to unscrew the little aerator fitting from the bathroom sink faucet, and temporarily install an adapter fitting to hook up the hose to. That lets you mix hot and cold water for refilling at much closer to the tank water temperature. That's the method I was using.