Automatic updates

[ConradSelig]

Currently the project runs as a "one and done" program, but wouldn't it be nice to have automatic updates for continual monitoring?

This should actually be pretty easy, as I did keep this feature in mind when completing #2.

Enabling this feature should be by command line argument only, and the default state of the program should still be that "one and done" run style.
The user should also be able to specify how often the refresh is done. New data comes in every minute from yfinance, so that should be the lower limit. I wrote a side script for myself that just re-runs this program from scratch every 5 minutes and I found that was a good starting point, maybe if there is a default refresh time we should set it there.