Easier early game and persistent data

I have made the game mechanics less challenging to start with, the enemy rng can still cause some bad runs, but the first few runs shouldn't end as quickly, which I think is more fun.

I have added a settings page to test the persisting of data, the volume control doesn't actually change the sound volume yet, but the value set should save and load each time the page is accessed.

I have also added saving of the player's 'best distance', it is still necessary to start from scratch with money and upgrades each time the game is loaded, but you can at least have a goal to reach for each play session.

The upgrade store also looks a bit nicer, I still need to add images for each upgrade, I will probably leave that for a while, as I am expecting the upgrades available to change.